Set ghcr.io username to user triggering the build

This should hopefully make pushes work in PRs? I'm grasping at straws at this point.

.github/workflows/main.yml

@@ -42,7 +42,7 @@ jobs:
         uses: docker/login-action@v1
         with:
           registry: ghcr.io
-          username: ${{ github.repository_owner }}
+          username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Build ${{ matrix.component }}