Make `PREVENT_STUCK_MODIFIERS` the default (#3107)
* Remove chording as it is not documented, not used, and needs work.
* Make Leader Key an optional feature.
* Switch from `PREVENT_STUCK_MODIFIERS` to `STRICT_LAYER_RELEASE`
* Remove `#define PREVENT_STUCK_MODIFIERS` from keymaps.
* Set up tap dance for layers on the lower button.
* Refactored code to share in the users directory between my two keyboard layouts.
* Small keyboard layout change.
* Updated documentation on oneshot usage in macros/tap dance.