[Feature request] Add multiple users at once

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### [Feature request] Add multiple users at once

**Is your feature request related to a problem? Please describe.**

I am trying to attribute multiple users with the same attributes, but I can't seem to attribute more than 1 user at a time [Reference](https://github.com/seanpm2001/All-Contributors_Test_Site/issues/1/)

**Describe the solution you'd like**

I would like to be able to add multiple users for the same contributions in a single pull request.

**Describe alternatives you've considered**

I don't know of any alternatives.

**Additional context**

I set up a little sandbox to test this, but it didn't work: https://github.com/seanpm2001/All-Contributors_Test_Site/issues/1/

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