gmmk/pro/mike1808 keymap (#13398)

* Add gmmk/pro/mike1808 keymap

* Add licenses

* Update readme

* Add underglow support for rgb matrix layers

* Change FN to TT

* Fix rgb layer disabling during rgb settings change

* also clean up some code

1 files changed, 19 insertions, 0 deletions

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+QMK layout for gmmk/pro
+=======================
+
+## Secrets
+The format is the same as [drashna's](../../../../users/drashna/readme_secrets.md) secrets implementation. Create a `secret.h` and define your secrets like this:
+
+```c
+static const char* secrets[] = {"secret1", "secret2", "secret3", "secret4", "secret5"};
+```
+
+## Rotary encoder knob
+You can hookup your encoder functions by defining new encoder states in [encoder.h](./encoder.h), then in [encoder.c](./encoder.c) assign static variable `state` your new state depending on your desired condition and add callbacks to `encoder_mapping` array. 
+
+## RGB Matrix Ledmaps
+RGB Matrix ledmaps is the future allowing you assign colors to individual keys on every keymap layer. 
+
+You can see some examples of my usage in the bottom of [keymap.c](./keymap.c).
+
+Color defines are just HSV colors wrapped in curly braces, like `#define RED { HSV_RED }`.