docker-test

Run the full test cycle for the spellcheck action: 1. Build the local Docker image: ```bash docker build -t jonasbn/github-action-spellcheck:local . ``` 2. Run all Bats tests against the local image: ```bash bats test/test.bats ``` 3. Report which tests passed or failed. If the Docker build failed, show the build error before proceeding. To run a single test by name, use: ```bash bats --filter "<test name>" test/test.bats ```