For a variety of reasons, including your Microsoft MVP activity reports, you might want to summarize your GitHub activity across multiple repos.
For contributors to Microsoft open-source docs on GitHub, all your contributions would end up in the MicrosoftDocs organization. Microsoft owns thousands of open-source repositories across many organizations, if you've contributed to others, variations on this same query work.
Absent a dashboard making this easier (keep an eye on this), here are some GitHub queries helpful to you.
You can find all merged PRs in public MicrosoftDocs org repositories using this search syntax on GitHub.com's main search bar:
is:pr author:<your GitHub username> is:public org:microsoftdocs merged:>=YYYY-MM-DD
For example:
is:pr author:williamadba is:public org:microsoftdocs merged:>=2019-01-01
Which results in the URL:
https://github.com/search?q=is%3Apr+author%3Awilliamadba+is%3Apublic+org%3Amicrosoftdocs+merged%3A%3E%3D2019-01-01&type=pullrequests
You can also use the GitHub API for programmatic access:
Feel free to comment if you have other preferred methods of tracking your Docs contributions on GitHub.com.