Add keyboard shadow80 (#22534)

Co-authored-by: Duncan Sutherland <dunk2k_2000@hotmail.com>

keyboards/pixelspace/shadow80/readme.md

@@ -0,0 +1,27 @@
+# Shadow80
+
+![shadow80](https://imgur.com/XLjjdMzh.jpg)
+An 80%/TenKeyLess sized keyboard with 74 RGB.
+Before enabling the maximum brightness of RGB lights, please confirm whether the USB device power supply supports it.
+This PCB has two versions: hotswap and solder.
+
+* Keyboard Maintainer: [PixelSpace](https://github.com/PixelSpaceStudio)
+* Hardware Supported: shadow80
+* Hardware Availability: [PixelSpace](https://github.com/PixelSpaceStudio)
+
+Make example for this keyboard (after setting up your build environment):
+
+    make shadow80:default
+       
+Flashing example for this keyboard:
+
+    make shadow80: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 2 ways:
+
+- **Bootmagic reset**: Hold down the key at (0,0)(always "ESC") in the matrix (usually the top left key which is Escape in this keyboard) and plug in the keyboard
+- **Keycode in layout**: Press the key mapped to `QK_BOOT`