Make workflow_dispatch Docker tag input required

#230 (comment)

Author: br3ndonland

.github/workflows/build-and-push-docker-image.yml

@@ -9,8 +9,8 @@ on:   # yamllint disable-line rule:truthy
   workflow_dispatch:
     inputs:
       tag:
-        description: Docker image tag (optional, defaults to Git ref)
-        required: false
+        description: Docker image tag
+        required: true
         type: string
 
 jobs: