Set exit_code correctly as output

[sebastiaanspeck]

Fixes #244

[mre]

Thanks! Can you also add a test which checks that the exit code works to https://github.com/lycheeverse/lychee-action/blob/master/.github/workflows/test.yml?

Something like that:

      - name: Test exit code output (expecting failure)
        id: lychee_exit_test
        uses: ./
        with:
          args: -- inputdoesnotexist
        continue-on-error: true

      - name: Check exit code
        run: |
          echo "Lychee exit code: ${{ steps.lychee_exit_test.outputs.exit_code }}"
          if [[ "${{ steps.lychee_exit_test.outputs.exit_code }}" == "1" ]]; then
            echo "Lychee correctly failed with exit code 1"
          else
            echo "Unexpected exit code: ${{ steps.lychee_exit_test.outputs.exit_code }}"
            echo "Expected exit code 1 for failed check"
            exit 1
          fi

[mre]

I think we need to test if lychee failed with an exit code other than 0 in case of error. Right now you're testing for 0, which is the default and should always work because otherwise the GitHub workflow stops. Did you try the code snippet I posted? 🤔

[mre]

lgtm thanks!