text: Title: [ENH]: Support avif as output format
  Body: ### Problem
  
  Since  v3.6.0, Matplotlib supports `webp` output (yay!), but I couldn't find a ticket tracking Avif support, so here's a feature request for `savefig` to support saving as `.avif`. 
  
  *relevant links:*
  - [CanIUse](https://caniuse.com/avif)
  - [Pillow pull request](https://github.com/python-pillow/Pillow/pull/5201)
  
  
  ### Proposed solution
  
  _No response_