[Keyboard] Add macro3 PCB support (#15131)

Co-authored-by: Joel Challis <git@zvecr.com>
Co-authored-by: Drashna Jaelre <drashna@live.com>
Co-authored-by: Ryan <fauxpark@gmail.com>
Co-authored-by: filterpaper <filterpaper@localhost>

keyboards/macro3/info.json

@@ -0,0 +1,20 @@
+{
+    "keyboard_name": "Macro3",
+    "url": "https://github.com/davidphilipbarr/Macropads/tree/main/macro3",
+    "maintainer": "@davidphilipbarr",
+    "layouts": {
+        "LAYOUT": {
+            "layout": [
+                {"x": 0, "y": 0},
+                {"x": 1, "y": 0},
+                {"x": 2, "y": 0},
+                {"x": 3, "y": 0},
+
+                {"x": 0, "y": 1},
+                {"x": 1, "y": 1},
+                {"x": 2, "y": 1},
+                {"x": 3, "y": 1},
+            ]
+        }
+    }
+}