Add automated reminder to update docs when updating freighter-api

[piyalbasu]

Create a CI pipeline that automatically reminds a dev to update documentation if it detects a change to freighter-api.

It should post a comment on the PR with the following message:

@stellar/freighter-api has been updated. Make sure to update the documentation in the [guide](https://github.com/stellar/freighter/tree/master/docs/docs/guide) and in the [playground](https://github.com/stellar/freighter/tree/master/docs/docs/playground)