feat: Agenda proposed badge

[holloway]

• Adds a grey 'Proposed' badge to sessions with a state of proposed.
  
• In dark mode darkens the 'BoF' badge to make it more readable. Before: . After: .

fixes #8026

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.93%. Comparing base (c7f6bde) to head (6c2bb07).
Report is 182 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8164      +/-   ##
==========================================
+ Coverage   88.78%   88.93%   +0.15%     
==========================================
  Files         296      303       +7     
  Lines       41320    41260      -60     
==========================================
+ Hits        36687    36696       +9     
+ Misses       4633     4564      -69     

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[rjsparks]

@cindymorgan : help us develop the right popup text?

[cindymorgan]

Suggest:

Proposed WGs are groups in the process of being chartered. If the charter is not approved by the IESG before the IETF meeting, the session may be canceled.

[holloway]

@rjsparks hah, I'd DMd Cindy yesterday to follow up about this too