feat(shields): Reviung34 shield definition

* Initial implementation of REVIUNG34 shield.
* Add copyright information to files
* Added a README with instructions on how to enable the 1x2u layout.
* Add a default chosen matrix transform in the default keymap, alongside a commented out version for the alternate layout.

---------

Co-authored-by: Peter Johanson <peter@peterjohanson.com>
Co-authored-by: Cem Aksoylar <caksoylar@users.noreply.github.com>

app/boards/shields/reviung34/boards/nice_nano_v2.overlay

@@ -0,0 +1,48 @@
+#include <dt-bindings/led/led.h>
+
+&pinctrl {
+    spi3_default: spi3_default {
+        group1 {
+            psels = <NRF_PSEL(SPIM_MOSI, 0, 6)>;
+        };
+    };
+
+    spi3_sleep: spi3_sleep {
+        group1 {
+            psels = <NRF_PSEL(SPIM_MOSI, 0, 6)>;
+            low-power-enable;
+        };
+    };
+};
+
+&spi3 {
+    compatible = "nordic,nrf-spim";
+    status = "okay";
+
+    pinctrl-0 = <&spi3_default>;
+    pinctrl-1 = <&spi3_sleep>;
+    pinctrl-names = "default", "sleep";
+
+    led_strip: ws2812@0 {
+        compatible = "worldsemi,ws2812-spi";
+        label = "WS2812";
+
+        /* SPI */
+        reg = <0>; /* ignored, but necessary for SPI bindings */
+        spi-max-frequency = <4000000>;
+
+        /* WS2812 */
+        chain-length = <9>; /* number of LEDs */
+        spi-one-frame = <0x70>;
+        spi-zero-frame = <0x40>;
+        color-mapping = <LED_COLOR_ID_GREEN
+                         LED_COLOR_ID_RED
+                         LED_COLOR_ID_BLUE>;
+    };
+};
+
+/ {
+    chosen {
+        zmk,underglow = &led_strip;
+    };
+};