ci: Pre-release workflows (#9366)

In preparation for the v0.37 release, this PR updates:
1. The [release guidelines](https://github.com/tendermint/tendermint/blob/thane/pre-release-workflows/RELEASES.md#pre-releases) regarding alpha and beta versions, as well as release candidates.
2. The GitHub workflows to build all 3 kinds of pre-releases for:
   1. Docker images
   2. Binaries (I'm still not 100% sure whether this is necessary, but it does act as a clear signal to users that a pre-release is available, and pre-built binaries could be useful for people running testnets who don't use Docker)
3. The Goreleaser config to auto-detect whether a tag is a pre-release and mark it as such as the release is created on GitHub.

---

#### PR checklist

- [x] Tests written/updated, or no tests needed
- [x] `CHANGELOG_PENDING.md` updated, or no changelog entry needed
- [x] Updated relevant documentation (`docs/`) and code comments, or no
      documentation updates needed

.github/workflows/docker.yml

@@ -6,8 +6,10 @@ on:
     branches:
       - main
     tags:
-      - "v[0-9]+.[0-9]+.[0-9]+"  # Push events to matching v*, i.e. v1.0, v20.15.10
-      - "v[0-9]+.[0-9]+.[0-9]+-rc*"  # Push events to matching v*, i.e. v1.0-rc1, v20.15.10-rc5
+      - "v[0-9]+.[0-9]+.[0-9]+"               # Push events to matching v*, i.e. v1.0, v20.15.10
+      - "v[0-9]+.[0-9]+.[0-9]+-alpha.[0-9]+"  # e.g. v0.37.0-alpha.1, v0.38.0-alpha.10
+      - "v[0-9]+.[0-9]+.[0-9]+-beta.[0-9]+"   # e.g. v0.37.0-beta.1, v0.38.0-beta.10
+      - "v[0-9]+.[0-9]+.[0-9]+-rc[0-9]+"      # e.g. v0.37.0-rc1, v0.38.0-rc10
 
 jobs:
   build:

.github/workflows/pre-release.yml

@@ -0,0 +1,40 @@
+name: "Pre-release"
+
+on:
+  push:
+    tags:
+      - "v[0-9]+.[0-9]+.[0-9]+-alpha.[0-9]+"  # e.g. v0.37.0-alpha.1, v0.38.0-alpha.10
+      - "v[0-9]+.[0-9]+.[0-9]+-beta.[0-9]+"   # e.g. v0.37.0-beta.1, v0.38.0-beta.10
+      - "v[0-9]+.[0-9]+.[0-9]+-rc[0-9]+"      # e.g. v0.37.0-rc1, v0.38.0-rc10
+
+jobs:
+  goreleaser:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - uses: actions/setup-go@v3
+        with:
+          go-version: '1.18'
+
+      - name: Build
+        uses: goreleaser/goreleaser-action@v3
+        if: ${{ github.event_name == 'pull_request' }}
+        with:
+          version: latest
+          args: build --skip-validate   # skip validate skips initial sanity checks in order to be able to fully run
+
+      # Link to CHANGELOG_PENDING.md as release notes.
+      - run: echo https://github.com/tendermint/tendermint/blob/${GITHUB_REF#refs/tags/}/CHANGELOG_PENDING.md > ../release_notes.md
+
+      - name: Release
+        uses: goreleaser/goreleaser-action@v3
+        if: startsWith(github.ref, 'refs/tags/')
+        with:
+          version: latest
+          args: release --rm-dist --release-notes=../release_notes.md
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}