Add links to release notes and commit diff in the PR

[Chris van Es]

On GitHub, when Dependaroo opens a pull request, it adds a subsequent comment to the PR which contains links to;

1. All of the release notes between your version and the newly proposed version of the given dependency.
2. A summary of the commits between your version and the newly proposed version of the given dependency. I believe it only provides a subset of the commits with a prefilled link to view the full diff (compare view) also provided.

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