Keymap: DZ60 layout based on stephengrier's with PgUp/PgDn/Home/End, Insert, etc...

Keymap: DZ60 layout based on stephengrier's with PgUp/PgDn/Home/End, Insert, etc. (#4110)

* DZ60 layout based on stephengrier's with customisations.

* CapsLock is used as Fn key.
* Del is available as Fn+Backspace & Shift+Backspace (using a macro)
* PgUp / PgDn / Home / End = Fn+Arrows (as on macOS, Microsoft Surface)
* Tilde = Shift+Esc
* Backtick = Fn+Esc
* Underglow toggle and mode selection are available as Fn+Q and Fn+W
* Reset (bootloader mode) = Fn+B

* Standardised layout formatting and Ctrl+Del & Shift+Del support.

Using 7 underscores for KC_TRNS in layouts and aligning the keycodes
according to LAYOUT_directional.

Del is now only Fn+Del, Ctrl+Backspace translates to Ctrl+Del,
Shift+Backspace translates to Shift+Del.

* Documented new Backspace/Del related macros.

Del is now just Fn+Backspace, pressing Ctrl+Backspace sends Ctrl+Del,
pressing Shift+Backspace sends Shift+Del