updating codecov.yml and README.md

[bobstrecansky]

This PR accomplishes two things:

• Fixes a couple typos and formatting issues in the README.md.
• Defines a codecov.yml, which makes codecov.io checks not required and updates the patch part of codecov.io to not execute. This was confusing to new maintainers and didn't provide a ton of value.

[codecov]

Codecov Report

Merging #338 (c02298e) into main (b658c96) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               main     #338   +/-   ##
=========================================
  Coverage     94.09%   94.09%           
  Complexity      552      552           
=========================================
  Files            49       49           
  Lines          1338     1338           
=========================================
  Hits           1259     1259           
  Misses           79       79           

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