Update readme.md

[rishabhj1717]

• Update method to fetch github_token from secrets
  • Earlier ${{ github.token }} was being used to get value of github_token, but it fails. Updated the readme to make it right, and made use of ${{ secrets.GITHUB_TOKEN }}
• Add example to merge branch with commit message

[rishabhj1717]

@MiguelSavignano Could you please let me know if this helps?

[MiguelSavignano]

@rishabhj1717 Thanks seems the new versions of Github actions did not allow ${{ github.token }} any more.

[rishabhj1717]

You're welcome @MiguelSavignano 😄 Yes, this was changed in the newer version.