add new parameter 'action'

[binary1230]

• Allow specifying alternative commands to run other than idf.py build
• Useful for using other esp-idf tools inside the docker container as part of Github CI builds.
• Defaults to idf.py build
• fixes #2

Example: Building custom flash images as part of Github actions

      - name: Create Final Merged Binary
        uses: espressif/esp-idf-ci-action
        with:
          esp_idf_version: v4.4
          path: './build/'

          # 'command' is the new thing this PR adds
          command: esptool.py --chip esp32 merge_bin --fill-flash-size 4MB -o ../your_custom_file.bin @flash_args

notes:

• Based on previous work by @BrianPugh
• I tested this with just my local projects, not sure if there's other test suites that it should be run through/etc
• Thanks everyone

[kumekay]

@binary1230 Thank you so much for the contribution!

I would only suggest naming the new parameter command instead of action`

Also, it looks like this closes https://github.com/espressif/esp-idf-ci-action/issues/2 could you please add fixes #2 to the PR description?

[binary1230]

changed and tested locally, works. should be good to go. thanks!

[kumekay]

@binary1230 Thank you for your contribution!