chore: add automated homebrew action (#2164)

* chore: add automated homebrew action

Signed-off-by: Christopher Phillips <christopher.phillips@anchore.com>

* migrate homebrew publish step to separate post-release workflow

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

---------

Signed-off-by: Christopher Phillips <christopher.phillips@anchore.com>
Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>
Co-authored-by: Alex Goodman <wagoodman@users.noreply.github.com>

.github/workflows/release-homebrew.yaml

@@ -0,0 +1,25 @@
+name: "Release Homebrew"
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  homebrew:
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Update Homebrew formula
+        uses: dawidd6/action-homebrew-bump-formula@d3667e5ae14df19579e4414897498e3e88f2f458 # v3.10.0
+        with:
+          token: ${{ secrets.HOMEBREW_TOKEN }}
+          org: anchore
+          formula: syft
+
+      - uses: 8398a7/action-slack@fbd6aa58ba854a740e11a35d0df80cb5d12101d8 #v3.15.1
+        if: ${{ failure() }}
+        with:
+          status: ${{ job.status }}
+          fields: repo,workflow,action,eventName
+          text: "Post-release homebrew publish workflow has failed: https://github.com/anchore/syft/actions/workflows/release-homebrew.yaml"
+        env:
+          SLACK_WEBHOOK_URL: ${{ secrets.SLACK_TOOLBOX_WEBHOOK_URL }}