feat(ci): add Lua formatting, translation validation, and test stages to CI pipeline

# GITLAB_TOKEN: A GitLab 'project access token' or 'personal access token' with `api`, `read_repository` and `write repository` scopes.

# SEMREL_GPG_SIGNKEY: Path to the GPG signkey exported with `gpg --armor --export-secret-key`.

lua-format-check:

  stage: test

  image: ghcr.io/johnnymorganz/stylua:latest

  rules:

    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'

  script:

    - echo "Checking Lua formatting with Stylua"

    - stylua --check bookloresync.koplugin test

msgfmt-check:

  stage: test

  image: alpine:latest

  rules:

    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'

  before_script:

    - apk add --no-cache gettext

  script:

    - echo "Validating gettext translation files"

    - |

      find "$CI_PROJECT_DIR/bookloresync.koplugin/locale" -name "*.po" | while read po; do

        mo="${po%.po}.mo"

        echo "Compiling $po -> $mo"

        msgfmt "$po" -o "$mo"

      done

lua-tests:

  stage: test

  image: alpine:latest

  rules:

    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'

  before_script:

    - apk add --no-cache bash git lua5.1 lua5.1-dev luarocks build-base

    - luarocks --lua-version=5.1 install busted

    - luarocks --lua-version=5.1 install luacov

    - luarocks --lua-version=5.1 install luacov-cobertura

  script:

    - echo "Running Lua test suite"

    - bash run_tests.sh

  artifacts:

    when: always

    paths:

      - luacov.report.out

      - coverage.xml

    expire_in: 10 days

build-koplugin-artifact:

  stage: build

  image: alpine:latest