add handwired/swiftrax/retropad (#10331)

* add retropad

* fix indicator leds

* fix bootmagic

* fix led indicators

* fix keymap

* fix keymap

* fix keymap

* fix keymap

* fix license headers

* Apply suggestions from code review

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

* Apply suggestions from code review

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

Co-authored-by: Swiftrax <swiftrax@gmail.com>
Co-authored-by: Drashna Jaelre <drashna@live.com>
Co-authored-by: Ryan <fauxpark@gmail.com>

keyboards/handwired/swiftrax/retropad/info.json

@@ -0,0 +1,12 @@
+{
+    "keyboard_name": "Retropad", 
+    "url": "https://github.com/swiftrax", 
+    "maintainer": "swiftrax", 
+    "width": 2, 
+    "height": 3.5, 
+    "layouts": {
+        "LAYOUT": {
+            "layout": [{"label":"0,1", "x":0.5, "y":0}, {"label":"1,0", "x":0, "y":1.5}, {"label":"1,1", "x":1, "y":1.5}, {"label":"2,0", "x":0, "y":2.5}, {"label":"2,1", "x":1, "y":2.5}]
+        }
+    }
+}