Add 2.2.x version alias for Django docs

[timgraham]

Details

• Project URL: https://readthedocs.org/projects/django/

Request

As in #4519, please add version 2.2.x as an alias for the stable/2.2.x branch just like have for other branches.

[humitos]

Hi @timgraham! I did this and triggered a build for this version at https://readthedocs.org/projects/django/builds/8822677/

The documentation will be served online at https://django.readthedocs.io/en/2.2.x/

I'm closing the issue, but feel free to let me know if something wen't wrong or anything.