[Keymap] Add pierrec83's gherkin keymap (#9465)

* [Keymap] Add pierrec83's gherkin keymap

Contribute my gherkin keymap upstream as it is semi-stable. It has grown
in symbiosis with my Kyria keymap which is already upstream.

Add a readme

* Remove generated keymap and instructions to generate it as it is done by qmk flash

keyboards/40percentclub/gherkin/keymaps/pierrec83/config.h

@@ -0,0 +1,31 @@
+#pragma once
+
+/* Make layout the right way:
+ *  - USB port on left side
+ *  - Switches facing the correct way
+ */
+#undef MATRIX_ROW_PINS
+#undef MATRIX_COL_PINS
+#define MATRIX_ROW_PINS { B6, B2, B3, B1, F7 }
+#define MATRIX_COL_PINS { D0, D4, C6, D7, E6, B4 }
+
+// Set the mouse settings to a comfortable speed/accuracy trade-off
+// Assume the screen refresh rate is 60 Htz or higher
+// The default is 50. This makes the mouse ~3 times faster and more accurate
+#define MOUSEKEY_INTERVAL 16
+// The default is 20. Since we made the mouse about 3 times faster with the previous setting,
+// give it more time to accelerate to max speed to retain precise control over short distances.
+#define MOUSEKEY_TIME_TO_MAX 40
+// The default is 300. Let's try and make this as low as possible while keeping the cursor responsive
+#define MOUSEKEY_DELAY 100
+// It makes sense to use the same delay for the mouseweel
+#define MOUSEKEY_WHEEL_DELAY 100
+// The default is 100
+#define MOUSEKEY_WHEEL_INTERVAL 50
+// The default is 40
+#define MOUSEKEY_WHEEL_TIME_TO_MAX 100
+
+#define TAPPING_TERM 200
+#define PERMISSIVE_HOLD
+#define IGNORE_MOD_TAP_INTERRUPT
+#define TAPPING_FORCE_HOLD