Add support for AVIF files in content

[jacbn]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 40.95%. Comparing base (809ae63) to head (ee140c7).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...va/uk/ac/cam/cl/dtg/isaac/api/IsaacController.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #810      +/-   ##
==========================================
- Coverage   40.96%   40.95%   -0.01%     
==========================================
  Files         550      550              
  Lines       23544    23546       +2     
  Branches     2835     2835              
==========================================
  Hits         9644     9644              
- Misses      13030    13032       +2     
  Partials      870      870              

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