Add CI workflow to lint shell scripts

Although currently very simple, the action setup script is essential to the proper funtioning of the action, so worthy
of some CI.

Author: per1234

.github/workflows/lint-shell.yml

@@ -0,0 +1,24 @@
+name: Lint shell scripts
+
+on:
+  push:
+    paths:
+      - '.github/workflows/lint-shell.yml'
+      - '**.sh'
+  pull_request:
+    paths:
+      - '.github/workflows/lint-shell.yml'
+      - '**.sh'
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      # Recursively lint all shell scripts in the repository
+      # See: https://github.com/azohra/shell-linter/blob/latest/README.md
+      - name: ShellCheck 
+        uses: azohra/shell-linter@latest

action-setup.sh

@@ -32,6 +32,7 @@ sudo apt-get install --yes python${PYTHON_PACKAGE_VERSION}-venv > /dev/null
 "$PYTHON_COMMAND" -m venv "$PYTHON_VENV_PATH"
 
 # Activate Python virtual environment
+# shellcheck source=/dev/null
 . "$PYTHON_VENV_ACTIVATE_SCRIPT_PATH"
 
 # Install Python dependencies