Add manual workflow dispatch to Docker image workflows

Enable manual triggering for api-push, package-push, and repo-push workflows
via the GitHub Actions UI by adding the workflow_dispatch event alongside
push on master. This allows running these workflows on demand.

Author: koki-develop

.github/workflows/api-push.yaml

@@ -1,5 +1,6 @@
 name: Publish API image
 on:
+    workflow_dispatch:
     push:
         branches:
             - master

.github/workflows/package-push.yaml

@@ -1,6 +1,7 @@
 name: 'Package Pushed'
 
 on:
+    workflow_dispatch:
     push:
         branches:
             - master

.github/workflows/repo-push.yaml

@@ -1,5 +1,6 @@
 name: Publish Repo image
 on:
+    workflow_dispatch:
     push:
         branches:
             - master