[Keyboard] Add Hub20 keyboard (#11497)

* add Hub20 support

* Keymap formatting cleanup

Co-authored-by: Ryan <fauxpark@gmail.com>

* Delete bootloader_defs.h as no longer required

* Correct make / flashing example

Co-authored-by: Ryan <fauxpark@gmail.com>

* Update rules.mk

Co-authored-by: Ryan <fauxpark@gmail.com>

Co-authored-by: Ryan <fauxpark@gmail.com>

keyboards/hub20/info.json

@@ -0,0 +1,36 @@
+{
+    "keyboard_name": "Hub20",
+    "keyboard_folder": "hub20",
+    "url": "https://github.com/joshajohnson/hub20",
+    "maintainer": "joshajohnson",
+    "width": 4,
+    "height": 6,
+    "layouts": {
+      "LAYOUT_all": {
+        "layout": [
+          {"label":"Mute", "x":0.5, "y":0},
+          {"label":"Play / Pause", "x":2.5, "y":0},
+          {"label":"-", "x":0, "y":1},
+          {"label":"*", "x":1, "y":1},
+          {"label":"/", "x":2, "y":1},
+          {"label":"Numlock", "x":3, "y":1},
+          {"label":"+", "x":0, "y":2},
+          {"label":"7", "x":1, "y":2},
+          {"label":"8", "x":2, "y":2},
+          {"label":"9", "x":3, "y":2},
+          {"label":"+", "x":0, "y":3},
+          {"label":"4", "x":1, "y":3},
+          {"label":"5", "x":2, "y":3},
+          {"label":"6", "x":3, "y":3},
+          {"label":"Enter", "x":0, "y":4},
+          {"label":"1", "x":1, "y":4},
+          {"label":"2", "x":2, "y":4},
+          {"label":"3", "x":3, "y":4},
+          {"label":"Enter", "x":0, "y":5},
+          {"label":".", "x":1, "y":5},
+          {"label":"0", "x":2, "y":5},
+          {"label":"0", "x":3, "y":5}
+        ]
+      }
+    }
+}