Only run diff-API workflow when releasing new versions

Author: fschutt

.github/workflows/check-public-api.yaml

@@ -4,9 +4,15 @@ env:
   RUST_BACKTRACE: 1
 on:
   push:
-    branches: [ "master" ]
-  pull_request:
-    branches: [ "master" ]   
+    branches:
+      - 'master'
+    tags:
+      # this is _not_ a regex, see: https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#filter-pattern-cheat-sheet
+      - '[0-9]+.[0-9]+.[0-9]+*'
+  workflow_dispatch:
+    inputs:
+      diff-api:
+          description: 'Diff API'
 jobs:
   setup:
     name: Set up