Unable to approve pr in the netlify-cms gui

**- Do you want to request a *feature* or report a *bug*?**
Feature

**- What is the current behavior?**
If the publish branch is a protected branch on GitHub, the content owner is unable to approve the pull request within the netlify-cms gui. Instead they have to go to GitHub and approve the pr there, which breaks their workflow experience.

**- What is the expected behavior?**
As most content teams are not developers or even tech savvy people, they should not be required to go into github to approve a pr, there should be a way to approve the changes within netlify-cms workflow itself.