feature: add install_repo property to draw-zmk.yml

Facilitates testing `keymap-drawer` PRs from a fork.

.github/workflows/draw-zmk.yml

@@ -44,6 +44,11 @@ on:
         default: false
         required: false
         type: boolean
+      install_repo:
+        description: 'Install keymap-drawer from a git repo. Primarily for testing changes using a keymap-drawer fork.'
+        default: 'caksoylar/keymap-drawer'
+        required: false
+        type: string
       install_branch:
         description: 'Install keymap-drawer from a git branch, use empty for pypi release (default)'
         default: ''
@@ -92,7 +97,7 @@ jobs:
 
       - name: Install keymap-drawer (git)
         if: inputs.install_branch != ''
-        run: python3 -m pip install "git+https://github.com/caksoylar/keymap-drawer.git@${{ inputs.install_branch }}"
+        run: python3 -m pip install "git+https://github.com/${{ inputs.install_repo }}@${{ inputs.install_branch }}"
 
       - name: Draw keymaps
         id: draw