[add] add workflow for creating the tag

Author: Alignof

.github/workflows/tag.yml

@@ -0,0 +1,21 @@
+name: Tag
+
+on:
+  push:
+    branches:
+      - master
+    paths:
+      - Cargo.toml
+
+jobs:
+  tag:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 2
+      - uses: salsify/action-detect-and-tag-new-version@v2
+        id: detect_tag
+        with:
+          create-tag: true
+          version-command: cargo read-manifest | jq -r .version