CI: Add ShellCheck for shell scripts

Author: kristapsk

.github/workflows/ci.yml

@@ -10,6 +10,8 @@ jobs:
             fetch-depth: 0
             fetch-tags: true
             submodules: recursive
+        - name: Run ShellCheck
+          uses: ludeeus/action-shellcheck@v4
         - name: Verify submodules
           run: git submodule status --recursive
         - name: Set up Zig

tools/fmt-check.sh

@@ -2,4 +2,4 @@
 set -e
 zig fmt --check .
 C_FILES=$(find ./src -type f -name '*.c' ! -name 'lv_font*')
-clang-format -style=file -dry-run -Werror $C_FILES
+clang-format -style=file -dry-run -Werror "$C_FILES"