Add a bit of CI.

.github/workflows/shellcheck.yml

@@ -0,0 +1,15 @@
+on:
+  push:
+    branch:
+      - master
+
+name: 'Trigger: Push action'
+
+jobs:
+  shellcheck:
+    name: Shellcheck
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Run ShellCheck
+      uses: ludeeus/action-shellcheck@master

.github/workflows/yamllint.yml

@@ -0,0 +1,12 @@
+name: 'Yamllint GitHub Actions'
+on:
+  - pull_request
+jobs:
+  yamllint:
+    name: 'Yamllint'
+    runs-on: ubuntu-latest
+    steps:
+      - name: 'Checkout'
+        uses: actions/checkout@master
+      - name: 'Yamllint'
+        uses: karancode/yamllint-github-action@master