Automate updating of homebrew casks (#2788)

Co-authored-by: pajlada <rasmus.karlsson@pajlada.com>

.github/workflows/homebrew.yml

@@ -0,0 +1,28 @@
+name: 'Publish Homebrew Cask on Release'
+on:
+  push:
+    tags:
+      # Should match semver for mainline releases (not including -beta)
+      - 'v2.[0-9]+.[0-9]+'
+      # TODO: handle beta and nightly releases
+      # Need to make those casks manually first
+      # - v2.[0-9]+.[0-9]+-beta(?:[0-9]+)
+
+env:
+  # This gets updated later on in the run by a bash script to strip the prefix
+  C2_CASK_NAME: 'chatterino'
+  C2_TAGGED_VERSION: '${{ github.ref }}'
+
+jobs:
+  update_stable_homebrew_cask:
+    name: 'Update the stable homebrew cask'
+    runs-on: 'macos-latest'
+    steps:
+      # Pulls out the version from the ref (e.g. refs/tags/v2.3.1 -> 2.3.1)
+      - name: 'Extract version from tag'
+        run: |
+            'STRIPPED_VERSION=$("refs/tags/$(C2_TAGGED_VERSION)" | sed "s/refs\/tags\/v//gm")'
+            'echo "C2_TAGGED_VERSION=$(STRIPPED_VERSION)" >> $GITHUB_ENV'
+      - name: 'Execute ''brew bump-cask-pr'' with version'
+        run: 'brew bump-cask-pr --version $(C2_TAGGED_VERSION) $(C2_CASK_NAME)'
+