Handle RTD enabling addons

[A5rocks]

Fixes #3064

I'm not sure whether this is required because the docs look fine, but then of course the docs have very many hacks that I'm not aware of.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.58915%. Comparing base (2a66a0d) to head (22d2bee). Report is 307 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main       #3103         +/-   ##
===================================================
+ Coverage   99.58714%   99.58915%   +0.00200%     
===================================================
  Files            121         121                 
  Lines          18166       18255         +89     
  Branches        3275        3314         +39     
===================================================
+ Hits           18091       18180         +89     
  Misses            52          52                 
  Partials          23          23                 

see 1 file with indirect coverage changes

[A5rocks]

OK I don't know why RTD is failing to clone this PR now...

[A5rocks]

Well it seems to work now. I'll merge this soon enough unless someone has comments.