git-artifacts: trigger on push

Now that we use GitHub-hosted Windows/ARM64 runners and do not have to
operate under the quite tight budget constraints of my personal Azure
account, we can make sure that we know whether `git-sdk-arm64` is in a
healthy state (read: whether we can build release artifacts without
problems).

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

.github/workflows/git-artifacts.yml

@@ -1,6 +1,9 @@
 name: git-artifacts
 
 on:
+  push:
+    branches:
+      - main
   workflow_dispatch:
 
 env: