[Keyboard] Adding Sunsetter R2 keyboard to Charue family (#17269)

Co-authored-by: Joel Challis <git@zvecr.com>
Co-authored-by: Drashna Jaelre <drashna@live.com>
Co-authored-by: Ryan <fauxpark@gmail.com>

keyboards/charue/sunsetter_r2/readme.md

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+# Sunsetter R2
+
+![Sunsetter R2](https://i.imgur.com/rQRuHRkh.jpeg)
+
+A 65 + 10% F-Key Column Keyboard kit made and sold by Charue Design.
+
+Round 2 includes RGB underglow, new case colors, a hotswap option, and a recessed USB port.
+
+[More info on charue-design.com](https://charue-design.com/)
+
+* Keyboard Maintainer: [ILWrites](https://github.com/PiKeeb)
+* Hardware Supported: [Sunsetter PCB](https://charue-design.com/collections/sunsetter)
+* Hardware Availability: [Charue Design](https://charue-design.com/)
+
+Make example for this keyboard (after setting up your build environment):
+
+    make charue/sunsetter_r2:default
+
+Flashing example for this keyboard:
+
+    make charue/sunsetter_r2:default:flash
+
+See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).
+
+## Bootloader
+
+Enter the bootloader in 3 ways:
+
+* **Bootmagic reset**: Hold down the key at (0,0) in the matrix (usually the top left key or Escape) and plug in the keyboard
+* **Physical reset button**: Briefly press the button on the back of the PCB - some may have pads you must short instead
+* **Keycode in layout**: Press the key mapped to `RESET` if it is available