ci: run devcontainer action on main

Previously it would only run on pull requests,
now it runs on any push to the affected files.

Author: johanbrandhorst

.github/workflows/devcontainer.yml

@@ -1,5 +1,5 @@
 on:
-  pull_request:
+  push:
     paths:
       - .devcontainer/devcontainer.json
       - .github/workflows/devcontainer.yml