Add support for specifying the target via the action yaml

[atanisoft]

This PR adds a new parameter to the action yaml which is used for specifying the ESP-IDF target to be used for the build.

Example run with mixed usage of ESP32 and ESP32-S3: https://github.com/atanisoft/ESP32CommandStation/actions/runs/1922997306

Syntax:

    strategy:
      max-parallel: 3
      matrix:
        target:
          - esp32-v4.4-L298
          - esp32-v4.4-LMD18200
          - esp32-v4.4-BTS7960B
          - esp32-v4.4-PCB
          - esp32-latest-L298
          - esp32-latest-LMD18200
          - esp32-latest-BTS7960B
          - esp32-latest-PCB
          - esp32s3-latest-PCB
    steps:
      - uses: actions/checkout@v2
        with:
          submodules: recursive
          fetch-depth: 0
      - uses: jungwinter/split@v2
        id: target
        with:
          msg: ${{ matrix.target }}
          separator: '-'
      - name: Configure default pin mapping
        run: |
          echo "CONFIG_ESP32CS_${{ steps.target.outputs._2 }}=y" > sdkconfig
      - name: Build
        uses: atanisoft/esp-idf-ci-action@main
        with:
          esp_idf_version: ${{ steps.target.outputs._1 }}
          esp_target: ${{ steps.target.outputs._0 }}

Fixes: https://github.com/espressif/esp-idf-ci-action/issues/5

This PR replaces: https://github.com/espressif/esp-idf-ci-action/pull/7.

[atanisoft]

@kumekay Can you review? This is a bit of a follow-up on your recent PR moving the version declaration to the actions yaml.

[kumekay]

@atanisoft Thank you for the PR!

[atanisoft]

Thanks for merging!