Add extra group for FastAPI

[patrick91]

Apparently marking a dependency as optional is not enough, you also need to create an extra group for it

Closes #1365

[codecov]

Codecov Report

Merging #1366 (7e5a046) into main (c6be3b4) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1366   +/-   ##
=======================================
  Coverage   98.12%   98.12%           
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  Files         113      113           
  Lines        3956     3956           
  Branches      568      568           
=======================================
  Hits         3882     3882           
  Misses         40       40           
  Partials       34       34           

[botberry]

Thanks for adding the RELEASE.md file!

Here's a preview of the changelog:

---

This release adds an extra dependency for FastAPI to prevent
it being downloaded even when not needed.

To install Strawberry with FastAPI support you can do:

pip install 'strawberry-graphql[fastapi]'

---

Here's the preview release card for twitter:

Here's the tweet text:

🆕 Release (next) is out! Thanks to Patrick Arminio for the PR 👏

Get it here 👉 https://github.com/strawberry-graphql/strawberry/releases/tag/(next)