refactor: Add more checks to pre-commit

Updated existing pre-commit hooks and added some new hooks:

- Remove trailing whitespace
- Ensure every non-empty file ends with a new line
- Check YAML file validity
- Prevent adding large files
- Ensure any scripts with shebangs are executable

Added a GitHub action to run pre-commit on every commit. Removed any
existing actions which duplicate pre-commit.

Ran pre-commit on the codebase.

app/boards/shields/elephant42/Kconfig.defconfig

@@ -15,7 +15,7 @@ if SHIELD_ELEPHANT42_LEFT || SHIELD_ELEPHANT42_RIGHT
 
 config ZMK_SPLIT
 	default y
- 
+
 if ZMK_DISPLAY
 
 config I2C

app/boards/shields/elephant42/elephant42.dtsi

@@ -3,7 +3,7 @@
  *
  * SPDX-License-Identifier: MIT
  */
- 
+
 #include <dt-bindings/zmk/matrix_transform.h>
 
 / {
@@ -36,7 +36,7 @@ RC(1,0) RC(1,1) RC(1,2) RC(1,3) RC(1,4) RC(1,5)                 RC(1,6) RC(1,7)
             , <&pro_micro 7 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>
             ;
 
-    }; 
+    };
 };
 
 &pro_micro_i2c {

app/boards/shields/elephant42/elephant42.keymap

@@ -3,7 +3,7 @@
  *
  * SPDX-License-Identifier: MIT
  */
- 
+
 #include <behaviors.dtsi>
 #include <dt-bindings/zmk/keys.h>
 #include <dt-bindings/zmk/bt.h>
@@ -19,7 +19,7 @@
 
     default_layer {
       bindings = <
-  &lt ADJT ESC  &kp Q &kp W &kp E     &kp R    &kp T                          &kp Y     &kp U    &kp I     &kp O   &kp P    &kp DEL 
+  &lt ADJT ESC  &kp Q &kp W &kp E     &kp R    &kp T                          &kp Y     &kp U    &kp I     &kp O   &kp P    &kp DEL
   &mt LCTRL TAB &kp A &kp S &kp D     &kp F    &kp G                          &kp H     &kp J    &kp K     &kp L   &kp SEMI &kp SQT
                 &kp Z &kp X &kp C     &kp V    &kp B                          &kp N     &kp M    &kp COMMA &kp DOT &kp FSLH
                             &kp LSHFT &mo LOWR &kp LGUI &kp BSPC    &kp SPACE &kp ENTER &mo RAIS &kp LALT

app/boards/shields/elephant42/elephant42_left.overlay

@@ -3,7 +3,7 @@
  *
  * SPDX-License-Identifier: MIT
  */
- 
+
 #include "elephant42.dtsi"
 
 &kscan0 {

app/boards/shields/elephant42/elephant42_right.overlay

@@ -3,7 +3,7 @@
  *
  * SPDX-License-Identifier: MIT
  */
- 
+
 #include "elephant42.dtsi"
 
 &default_transform {