[Keyboard] Add arc60 (#17976)

Co-authored-by: Drashna Jaelre <drashna@live.com>

keyboards/vertex/arc60/readme.md

@@ -0,0 +1,22 @@
+# arc60
+
+* A customizable soldering 60% keyboard.
+
+* Keyboard Maintainer: [EASON](https://github.com/EasonQian1)
+* Hardware Supported: arc60
+* Hardware Availability: [vertex-kb](https://github.com/Vertex-kb)
+
+Make example for this keyboard (after setting up your build environment):
+
+    make vertex/arc60:default
+
+Flashing example for this keyboard:
+
+    make vertex/arc60: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 Enter in the keyboard then replug
+* **Physical reset button**: Briefly press the button on the back of the PCB
+* **Keycode in layout**: Press the key mapped to `RESET`