Fix NuGet badges

[martincostello]

Use shields.io for NuGet badges.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.30%. Comparing base (7e49266) to head (d207576).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #885   +/-   ##
=======================================
  Coverage   99.30%   99.30%           
=======================================
  Files          15       15           
  Lines         868      868           
  Branches      198      198           
=======================================
  Hits          862      862           
  Misses          4        4           
  Partials        2        2           

Flag	Coverage Δ
linux	99.30% <ø> (ø)
macos	99.30% <ø> (ø)
windows	99.30% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.