Keymap: Add am keymap (#3843)

Keymap: Add am keymap (#3843)

* Add am keymap

* Add configuration to play nice with stuck modifiers

This is in particular useful with emacs since its easy to get ctrl stuck

* Deactivate mouse keys and backlight

* Add control/esc and shift/enter taps

* Remove DVORAK and PLOVER

I won't be using this soon, so getting some free space

* Raiser and Lower ideas from jeebak

* Add cursor and mouse layers

* Enable mouse keys

* Switch underscore with minus

* Disable audio and fix warnings

* Update to the upstream changes

* VIM line motion symbols on the raise layer

* Enable sound and freeup some media keys on layers

* Fix whitespace on keymap

* Code review changes

* Improve keymap documentation

* Improve keymap to match to the default one

* Restore DEFAULT_FOLDER to the default value

* Fix config.h unescaped line