Update README with some onboarding updates, contributing instructions

[mofojed]

• Clean up some instructions
• Add cla.yml for enabling clabot
• Removed references to Enterprise - Enterprise depends on Community, not the other way around.

[codecov]

Codecov Report

Merging #533 (33e3623) into main (944d078) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #533   +/-   ##
=======================================
  Coverage   36.38%   36.38%           
=======================================
  Files         390      390           
  Lines       28502    28503    +1     
  Branches     6728     6730    +2     
=======================================
+ Hits        10370    10371    +1     
  Misses      17786    17786           
  Partials      346      346           

Flag	Coverage Δ
unit	36.38% <ø> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
...nditional-formatting/ConditionalFormattingUtils.ts	25.51% <0.00%> (+0.19%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 944d078...33e3623. Read the comment docs.