shellcheck.yml: Add check at every pull request

Shellcheck 2.0.0 is launched on every pull request.
Two warnings were ignored :
SC2154 - var is referenced but not assigned
SC2086 - Double quote to prevent globbing and word splitting

Respect these warning will make the code much messier and hard to read.

Signed-off-by: Erwann Roussy <[email protected]>

Author: eroussy

.github/workflows/shellcheck.yml

@@ -0,0 +1,16 @@
+name: "ShellCheck"
+
+on:
+  pull_request:
+    types: [opened, reopened, synchronize]
+
+jobs:
+  shellcheck:
+    name: Shellcheck
+    runs-on: ubuntu-latest
+    steps:
+        - uses: actions/checkout@v3
+        - name: ShellCheck
+          uses: ludeeus/[email protected]
+          env: 
+            SHELLCHECK_OPTS: -e SC2086 -e SC2154