Add "ci" and "publish" workflows

The `ci` workflow will trigger the others appropriately, depending
whether it is a release (semver tag), or a pull request or a push to
master

.github/workflows/check.yml

@@ -1,11 +1,6 @@
-name: Check `healm`
+name: Check
 on:
-  push:
-    branches:
-      - master
-  pull_request:
-    branches:
-      - master
+  workflow_call:
 
 jobs:
   test:

.github/workflows/ci.yml

@@ -0,0 +1,24 @@
+name: CI
+
+on:
+  pull_request:
+    branches:
+      - master
+  push:
+    branches:
+      - master
+    tags:
+      - v*.*.*
+
+jobs:
+  check:
+    uses: ./.github/workflows/check.yml
+
+  publish:
+    uses: ./.github/workflows/publish.yml
+    if: github.event_name == 'push' && contains(github.ref, 'refs/tags/')
+    needs: check
+    with:
+      version: ${{ github.ref }}
+    secrets:
+      crates-io-token: ${{ secrets.CRATES_IO_TOKEN }}

.github/workflows/publish.yml

@@ -0,0 +1,28 @@
+name: Publish
+on:
+  workflow_call:
+    inputs:
+      version:
+        description: 'Semver of the version to publish'
+        type: string
+        required: true
+    secrets:
+      crates-io-token:
+        description: 'Token for publishing to crates.io'
+        required: true
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    container:
+      image: rust:latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: check manifest version
+        run: |
+            version=$(grep -oP '(?<=^version = ").*(?="$)' Cargo.toml)
+            if [ "$version" != "${{ inputs.version }}" ]; then
+                echo "Version mismatch: Cargo.toml version is $version, but workflow input version is ${{ inputs.version }}"
+                exit 1
+            fi
+      - run: cargo publish --token ${{ secrets.crates-io-token }} --dry-run