Release Helm charts via helm/chart-releaser GHA

Use the official Helm chart releasing GitHub Action instead of our
custom bash.

Travis CI can be removed after this commit, as all tests will have
equivalents for GHAs.

Closes: #71
Signed-off-by: Daniel Farrell <dfarrell@redhat.com>

.github/workflows/release.yml

@@ -0,0 +1,25 @@
+---
+name: Release Charts
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  release:
+    name: Release
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Configure Git
+        run: |
+          git config user.name "$GITHUB_ACTOR"
+          git config user.email "$GITHUB_ACTOR@users.noreply.github.com"
+
+      - name: Run chart-releaser
+        uses: helm/chart-releaser-action@v1
+        env:
+          CR_TOKEN: "${{ secrets.GITHUB_TOKEN }}"