Resolve "Implement gitmailmap"

Now the sorted output can be seen by typing: git shortlog -sne

There is a 4+ year issue about Gitlab not respecting gitmailmap

• https://gitlab.com/gitlab-org/gitlab/-/issues/14909
• it seems it is going to be resolved soon and we might see it correctly displaying in Gitlab UI
  https://gitlab.com/gitlab-com/marketing/community-relations/contributor-program/gsoc-2022/-/issues/4

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Closes #127 (closed)