Duplicate people in contributors list

[rojvv]

Bug report

Description

There will be different items in the contributors list pointing to the same people if someone commits under two names.

Steps to reproduce

1. Edit a markdown file.
2. git add
3. git commit --author "Foo <foo@bar.org>
4. Edit the edited markdown file again.
5. git add
6. git commit --author "Foo Bar <foo@bar.org>

Expected behavior

Count authors with their emails, merge them if the names were duplicate in different commits.

[meteorlxy]

Users could handle the contributors list according to their needs in extendsPageData hook