Automate releases using GHA

To publish a release, we currently have to run `make docker-run-release` locally after tagging a release, which is not a huge effort but a bit cumbersome, because we do it only a few times a year and that is long enough to lose my memory :)

Starting this change, we use a GHA workflow to automatically build and publish binaries whenever a new semver tag is created, so that we do not need to run `make` anymore.

.github/workflows/release.yaml

@@ -0,0 +1,37 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - '*'
+
+permissions:
+  contents: write
+
+jobs:
+  goreleaser:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        if: ${{ !startsWith(github.ref, 'refs/tags/v') }}
+        run: echo "flags=--snapshot" >> $GITHUB_ENV
+      -
+        name: Checkout
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+      -
+        name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: '1.20.12'
+          cache: true
+      -
+        name: Run GoReleaser
+        uses: goreleaser/goreleaser-action@v4
+        with:
+          distribution: goreleaser
+          version: latest
+          args: release --clean ${{ env.flags }}
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.goreleaser.yml

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+project_name: helm-diff
+builds:
+  - id: default
+    main: .
+    binary: bin/diff
+    env:
+      - CGO_ENABLED=0
+    flags:
+      - -trimpath
+    ldflags:
+      - -X github.com/databus23/helm-diff/v3/cmd.Version={{ .Version }}
+    goos:
+      - freebsd
+      - darwin
+      - linux
+      - windows
+    goarch:
+      - amd64
+      - arm64
+
+archives:
+  - id: default
+    builds:
+    - default
+    format: tgz
+    name_template: '{{ .ProjectName }}-{{ if eq .Os "darwin" }}macos{{ else }}{{ .Os }}{{ end }}-{{ .Arch }}'
+    files:
+    - README.md
+    - plugin.yaml
+    - LICENSE
+changelog:
+  use: github-native
+
+release:
+  prerelease: auto