feat(shields): Add elephant42 Shield Support (#1009)

* Initial Elephant42 implementation

* Add underglow feature

* Fix keymap

* Copy corne defconfig for OLED and LED

* Fix matrix positions

* Add nice_nano_v2.overlay

* Usability improvements to keymap

* Update LED length

* Delete nice_nano v1 overlay

* Remove unused conf files

* Add copyright/license headers

* PR feedback

* Try fixing formatting again

* Minor format

* More missed tabs

* Format

app/boards/shields/elephant42/elephant42.zmk.yml

@@ -0,0 +1,14 @@
+file_format: "1"
+id: elephant42
+name: Elephant42
+type: shield
+url: https://github.com/illness072/elephant42
+requires: [pro_micro]
+exposes: [i2c_oled]
+features:
+  - keys
+  - display
+  - underglow
+siblings:
+  - elephant42_left
+  - elephant42_right