docs: fix & update badges

[agilgur5]

Summary

Fix badges and update a tiny bit to be more consistent with what I use today

• Similar to https://github.com/agilgur5/mst-persist/pull/35

Details

• update/fix "build status" badge according to Shields directions: https://github.com/badges/shields/issues/8671

• remove old nodei.co badge

  • doesn't always load and isn't very useful anymore
  • removing it from all of my NPM projects

• also change Installation to a codeblock instead of just backticks

  • easier to read as a block and easier to copy (full horizontal length)
  • and more consistent too

[codecov[bot]]

Codecov Report

Merging #99 (d210c1e) into main (64c7c49) will not change coverage. The diff coverage is n/a.

@@            Coverage Diff            @@
##              main       #99   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines           75        75           
  Branches         9         9           
=========================================
  Hits            75        75