move spaceholdings boards into /spaceholdings (#16096)

keyboards/spaceholdings/nebula68b/readme.md

@@ -0,0 +1,32 @@
+# Nebula68B
+
+This is a standard fixed layout 68% PCB. It supports VIA, full per-key RGB and underglow RGB. This is revision B.
+
+* Keyboard Maintainer: [Yiancar](http://yiancar-designs.com/) and on [GitHub](https://github.com/yiancar)
+* Hardware Supported: A 68% keyboard with ATMEGA32U4
+* Hardware Availability: https://spaceholdings.net/
+
+## Instructions
+
+### Build
+
+Make example for this keyboard (after setting up your build environment):
+
+    make spaceholdings/nebula68b:via
+
+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).
+
+### Reset
+
+- Unplug
+- Hold Escape
+- Plug In
+- Unplug
+- Release Escape
+
+### Flash
+
+- Unplug
+- Hold Escape
+- Plug In
+- Flash using QMK Toolbox or dfu-util (`make nebula65b:<keymap>:flash`)