[DOC] Add Codecov coverage testing

[slumnitz]

• add Codecov badge to README.md
• add .codecov.yml after Numpy example

[jGaboardi]

Anything more I can help out with for this?

[slumnitz]

@jGaboardi I'll be sprinting on this again on Monday, would you be interested interested in another work along session like last time? :)

[jGaboardi]

@jGaboardi I'll be sprinting on this again on Monday, would you be interested interested in another work along session like last time? :)

I'll probably be able to do that and will absolutely join if I can.

[martinfleis]

@jGaboardi do you recall what needs to be done here (if something)?

[jGaboardi]

Although not required, I would like to see some changes to .codecov.yml:

• probably rename to codecov.yml
• in the notify section increase the after_n_builds value to however many builds are actually being performed
• add an after_n_builds variable to the comments section (same value as previous bullet)
• add a range to the coverage section
• and other details (here is spaghetti's, for example)

[martinfleis]

@jGaboardi can you push those? It seems you have a clear idea what to do. We'll get it out of the way and make that patch release with #140, which is well overdue.

[jGaboardi]

Should we also put in another PR for trimming down the CI matrix?

[jGaboardi]

@martinfleis, Do you want to resolve the README conflicts or shall I?

[martinfleis]

Thanks both!

[codecov]

Codecov Report

Merging #127 (cacf532) into main (3121b26) will increase coverage by 0.6%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##            main    #127     +/-   ##
=======================================
+ Coverage   75.8%   76.4%   +0.6%     
=======================================
  Files         19      19             
  Lines       1570    1570             
=======================================
+ Hits        1190    1199      +9     
+ Misses       380     371      -9     

Impacted Files	Coverage Δ
splot/_version.py	40.7% <0.0%> (+2.7%)	⬆️