Fix broken images and add new banners

[zoek1]

Description

Only update images and fix broken images on email (convert svg image to png)

Refers/Fixes

Testing

[jdorfman]

This will address the most important accessibility issues for The Weekly Mint. cc @owocki

[codecov]

Codecov Report

Merging #7523 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7523      +/-   ##
==========================================
+ Coverage   26.07%   26.09%   +0.01%     
==========================================
  Files         310      310              
  Lines       31067    31067              
  Branches     4598     4598              
==========================================
+ Hits         8100     8106       +6     
+ Misses      22688    22682       -6     
  Partials      279      279              

Impacted Files	Coverage Δ
app/dashboard/embed.py	31.60% <0.00%> (+3.44%)	⬆️

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