[Keymap] New Massdrop ALT keymap for emptyflask (#8460)

amended to remove a couple of unnecessary lines,
thanks to @zvecr and @fauxpark

keyboards/massdrop/alt/keymaps/emptyflask/README.md

@@ -0,0 +1,14 @@
+### Drop (Massdrop) ALT Layout
+
+This layout is for the [Drop ALT Keyboard](https://drop.com/buy/massdrop-alt-high-profile-mechanical-keyboard).
+
+Features:
+
+* Tap caps lock for ESC, hold for CTRL
+* Prefer grave/tilde to dedicated ESC key
+* Swap home and delete. It's more compatible with my keycaps, and closer to a traditional layout.
+* Numpad layer (FN-\ to enable)
+* Method for clearing all stuck-down mods (taken from favorable-mutation, for tapped modifiers)
+
+To do:
+* Customize RGB: solid colors by default, highlight numpad keys when using that layer.