[Keymap] Adding personal keymap / clarifying default keymap readme (#6119)

* Adding led support for Plaid

* Adding led support for Plaid

* Update readme.md

Fixing bad markdown

* Adding my personal keymap

* Clarifying LED instructions / formatting

keyboards/plaid/keymaps/brickbots/readme.md

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+# Brickbots keymap for plaid
+Original copyright 2019 Takuya Urakawa (dm9records.com)
+LED Support added by Richard Sutherland (rich@brickbots.com)
+
+This layout is based on the Planck layout, with esc/tab swapped and an extra
+ctrl key in the bottom left corner. It includes an adjust layer (6)
+accessible by holding the lower and raise modifiers (MO3 and MO4) together.
+The adjustment layer is used to set the behavior of the two LEDs:
+
+**Modifier Mode:**   
+Activates when any modifier (shift, alt, os, MO) key is held
+down.  LED turns off when key is release
+
+**Blinkinlights Mode:**  
+Random chance of state change on each keystroke.
+
+**Keypress Mode:**  
+On for any keypress as long as the key is pressed
+
+**Carriage Mode:**  
+Turns on when enter is pressed, turns off when any next key is pressed
+
+To set the behavior of an LED, and save it to eeprom, hold the
+raise/lower keys together to access the adjust layer, then use
+the keys indicated below to set the behaviors
+
+* q = Toggle Red LED state, deactivates any other modes
+* w = Toggle Green LED state, deactivates any other modes
+* e = Set RED LED to modifier mode
+* r = Set GREEN LED to modifier mode
+* t = Set RED LED to Blinkinlights mode
+* y = set GREEN LED to Blinkinlights mode
+* u = set RED LED to Keypress mode
+* i = set GREEN LED to Keypress mode
+* o = set RED LED to Carriage mode
+* p = set GREEN LED to Carriage mode