[Keymap] Clean up my ergo keymaps and userspace (#8857)

* Remove more mouse keys settings missed in #8836

* Turn off more unwanted make options

* clang-format my userspace

* Reword ergo layout docs so Crkbd is canonical

* Add a basic readme to my userspace

* Tweak Crkbd readme wording and fix typos

* Enable SPLIT_USB_DETECT for Lily58 w/ Elite-C bug

keyboards/crkbd/keymaps/bcat/readme.md

@@ -1,9 +1,24 @@
 # bcat's Corne layout
 
-This split ergo layout mirrors
-[my Lily58 layout](https://github.com/qmk/qmk_firmware/tree/master/keyboards/lily58/keymaps/bcat)
-with the number row removed and RGB controls added. See that layout's docs for
-more details on the principles that went into the layout.
+This is my favorite split ergo layout for typing, featuring the traditional
+four ortho/ergo layers (Default, Lower, Raise, Adjust). It is loosely inspired
+by the default Planck (numbers on Lower, symbols on Raise) and Crkbd (Space on
+left, Enter on right) layouts, but has since been redesigned heavily according
+to the principles described below:
+
+* Since most of the modifiers are on the left half, keys frequently pressed
+together with mods (e.g., numbers, function keys, etc.) are on the Raise layer
+activated by the right thumb.
+
+* Navigation can be done on the right half alone, to enable simultaneous
+left-handed mousing. Additionally, Web pages can be scrolled with Space or
+Shift+Space on the left half alone, to enable taking notes with the right hand
+at the same time.
+
+* Other than Right Shift (which I seldom use), mods aren't rebound on layers.
+
+* Likewise, Backspace is not rebound on layers to avoid having to let go of
+layer-switch keys to correct mistakes.
 
 ## Default layer
 
@@ -11,20 +26,97 @@ more details on the principles that went into the layout.
 
 ([KLE](http://www.keyboard-layout-editor.com/#/gists/08d9827d916662a9414f48805aa895a5))
 
+* The alpha keys are a standard QWERTY layout, no funny business there.
+
+* Tab and Backspace are in familiar locations from my row-staggered boards
+(almost all of which use HHKB-style split backspace).
+
+* Likewise, the Ctrl key is in the same place as on my row-staggered boards
+(where I've been remapping Caps Lock as Ctrl since before even using QMK).
+
+* There are two Shift keys, because I do use Right Shift on occasion (even
+though I'm predominately a Left Shift-er).
+
+* Lower and Raise layer-switch keys are below the left and right thumb,
+respectively, when resting my fingers on the home row.
+
+* Space and Enter are on the big thumb keys so they're easy to press.
+
+* Alt is on the left so I can navigate back (Alt+Raise+H) and forward
+(Alt+Raise+L) without having to uncomfortably hit two thumb keys on the same
+half. This puts Super on the right by the process of elimination.
+
+* Escape shares a mod-tap key with Ctrl, which is convenient for Vim, but not
+something I'm totally in love with, as even after tweaking `TAPPING_TERM` I
+still get occasional spurious Esc taps. (I might move Esc up a key and put Tab
+on a layer, but that'd take some getting used to....)
+
 ## Lower layer
 
 ![Lower layer layout](https://i.imgur.com/rDlSmrA.png)
 
 ([KLE](http://www.keyboard-layout-editor.com/#/gists/c3fba5eaa2cd70fdfbdbc0f9e34d3bc0))
 
+* This could also be called the "symbol layer".
+
+* Shifted numbers are bound in their usual positions on the top row.
+
+* Hyphen/Underscore and Equals/Plus are in the right index- and middle-finger
+columns for easy reach. They share the same relative position as on a
+row-staggered keyboard, and the shifted versions are physically above the
+unshifted versions as a mnemonic device.
+
+* Brackets and braces are placed below the parens for easy recall. Once again,
+the shifted versions are on the home row and the unshifted versions are on the
+bottom row.
+
+* Forward Slash/Pipe and Backtick/Tilde fill out the remaining positions on the
+right half, with the same relative positions as on a row-staggered HHKB layout.
+And yup, the shifted versions are above the unshifted versions.
+
+* Caps Lock is bound in the same position as on an HHKB, for lack of an obvious
+better location.
+
+* Some extra keys are placed on the bottom row of the left half, ensuring every
+key on a TKL has a binding.
+
+* The left-half home row is reversed for future use. (It's free real estate.)
+
 ## Raise layer
 
 ![Raise layer layout](https://i.imgur.com/cVoKygg.png)
 
 ([KLE](http://www.keyboard-layout-editor.com/#/gists/08b44355d4ca85d294bad9e2821f91d7))
 
+* This could also be called the "number layer".
+
+* Unshifted numbers are bound in their usual positions on the top row.
+
+* Arrow keys are on VIM-style HJKL keys.
+
+* Home/End and Page Up/Page Down are in the same column as the arrow keys, but
+translated down one row. (This means that the comma and period keys are not
+bound on the number layer, which makes data entry a bit funky. I might add a
+dedicated numpad layer to compensate.)
+
+* Function keys F1–F10 take up most of remaining space on the left half, with
+F11 and F12 spilling over to the right half. (This puts the most used function
+keys (F1–F5) on the home row.)
+
+* Insert and Delete are on the rightmost column, because there didn't seem to
+be a better place to put them.
+
 ## Adjust layer
 
 ![Adjust layer layout](https://i.imgur.com/LEHM4DU.png)
 
 ([KLE](http://www.keyboard-layout-editor.com/#/gists/77e7572e077b36a23eb2086017e16fee))
+
+* Media keys are centered around the ESDF cluster, just like I arrange them on
+row-staggered keyboards. (It's even more sensible with columnar stagger.)
+
+* The navigation keys are replaced by RGB controls. Again, this mirrors the
+positioning I use on my row-staggered keyboards.
+
+* Finally, reset keys live at the top-left corner of the right half where it's
+reasonably hard to press them by accident.