[Keyboard] Add rb87 (#19546)

keyboards/ryanbaekr/rb87/readme.md

@@ -0,0 +1,19 @@
+# rb87
+
+A diy stacked acrylic 80% keyboard. 
+
+* Keyboard Maintainer: [ryanbaekr](https://github.com/ryanbaekr)
+* Hardware Supported: rb87 with Elite-C
+* Hardware Availability: 2022/12/30
+
+Make example for this keyboard (after setting up your build environment):
+
+    make ryanbaekr/rb87:default
+
+Flashing example for this keyboard:
+
+    make ryanbaekr/rb87:default:flash
+
+To boot into the bootloader, hold the reset button on the Elite-C on plug in
+
+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).