replace httpstatuses.com with httpstatuses.io

[collinstevens]

https://httpstatuses.com was taken down in early 2022 per https://jkulton.com/2022/reviving-httpstatuses.

This replaces https://httpstatuses.com with https://httpstatuses.io which presents the route structure and information.

The new https://httpstatuses.io website source code is located at https://github.com/httpstatuses/httpstatuses.

[codecov]

Codecov Report

Merging #173 (5f155a9) into master (48b8d9e) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #173   +/-   ##
=======================================
  Coverage   85.87%   85.87%           
=======================================
  Files          31       31           
  Lines        1097     1097           
=======================================
  Hits          942      942           
  Misses        155      155           

Impacted Files	Coverage Δ
src/ProblemDetails/StatusCodeProblemDetails.cs	81.81% <100.00%> (ø)

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[khellang]

Ah, thanks! This closes #167