feat: Add commitMessage option

[peaceiris]

Close #74
cf. #72 and #73

TODO

• Update README

[peaceiris]

@fabiosangregorio Please try the following.

- name: Deploy
  uses: peaceiris/actions-gh-pages@v2.9.0-0
  env:
    ...
  with:
    commitMessage: ${{ github.event.commits[0].message }}

[fabiosangregorio]

This is perfect! I tested it out and it works as expected. Thank you so much.

[peaceiris]

v2.9.0 has been released and the v2 tag updated. We can use the commitMessage option with the v2 tag.

- name: Deploy
  uses: peaceiris/actions-gh-pages@v2
  env:
    ...
  with:
    commitMessage: ${{ github.event.commits[0].message }}

[peaceiris]

I found head_commit, it is better.

commitMessage: ${{ github.event.head_commit.message }}