Add PNG and JPEG files to LFS automatically

[davorrunje]

Why are these changes needed?

Large binary files such as PNG and JPEG files are often added to the repository directly and not using LFS. This PR adds automatic filters for tracking PNG and JPEG files using LFS. It also moves already committed files to FLS.

Related issue number

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 37.83%. Comparing base (989c182) to head (b96bc57).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2226   +/-   ##
=======================================
  Coverage   37.83%   37.83%           
=======================================
  Files          77       77           
  Lines        7766     7766           
  Branches     1663     1663           
=======================================
  Hits         2938     2938           
  Misses       4579     4579           
  Partials      249      249           

Flag	Coverage Δ
unittests	37.81% <ø> (ø)

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