feat: add hook scripts support

2. use any programmatic solution of your choice with a JavaScript-based [configuration file](https://github.com/GoogleChrome/lighthouse-ci/blob/main/docs/configuration.md#configuration-file).

3. explicitly set the `collect.url` option in the `LHCI_RUN_OPTS` variable (hardcoded to a single server),

### Hook scripts

The Lighthouse template supports _optional_ **hook scripts** from your project, located in the root directory to perform additional project-specific logic:

* `pre-lighthouse.sh` is executed **before** running Lighthouse,

* `post-lighthouse.sh` is executed **after** running Lighthouse (whichever the tests status).

## Examples

### Analysing multiple urls

    log_info "... done"

  }

  function maybe_exec_hook() {

    if [[ -f "$1" ]]

    then

      log_info "\\e[33;1m$1\\e[0m hook found: execute"

      if [[ ! -x "$1" ]] && ! chmod +x "$1"

      then

        log_warn "... could not make \\e[33;1m${1}\\e[0m executable: please do it (chmod +x)"

        # fallback technique

        sh "$1"

      else

        "$1"

      fi

    fi

  }

  function awkenvsubst() {

    # escapes '&' char in variables for gsub

    awk '{while(match($0,"[$%]{[^}]*}")) {var=substr($0,RSTART+2,RLENGTH-3);val=ENVIRON[var];gsub("&","\\\\&",val);gsub("[$%]{"var"}",val)}}1'

    - install_ca_certs "${CUSTOM_CA_CERTS:-$DEFAULT_CA_CERTS}"

    - npm install -g @lhci/cli@$LHCI_VERSION

  script:

    # maybe execute pre hook

    - maybe_exec_hook "./pre-lighthouse.sh"

    # run tests

    # late variables expansion (to expand propagated $environment_url)

    - lhci_run_args=$(echo "$LHCI_RUN_OPTS" | awkenvsubst)

    - lhci autorun $lhci_run_args

    - lhci autorun $lhci_run_args || rc=$?

    # maybe execute post hook

    - maybe_exec_hook "./post-lighthouse.sh"

    # exit with return code

    - exit $rc

  artifacts:

    name: "$CI_JOB_NAME artifacts from $CI_PROJECT_NAME on $CI_COMMIT_REF_SLUG"

    when: always