chore: add funding field to package.json

[armano2]

This PR removes opencollective-postinstall that was used only during dev build and adds a funding field to the package.json so users installing will know how to contribute.

This is a new feature as of npm version 6.13.

See:

• https://medium.com/npm-inc/npm-weekly-222-announcing-lots-of-launches-2de4bd670340
• https://github.com/npm/rfcs/blob/latest/accepted/0017-add-funding-support.md

[bradzacher]

probably also want to add it to every single one of our packages.

[armano2]

probably also want to add it to every single one of our packages.

i added it to all public packages except tslint as this is only wrapper

[codecov]

Codecov Report

Merging #1499 into master will decrease coverage by 0.01%.
The diff coverage is 94%.

@@            Coverage Diff             @@
##           master    #1499      +/-   ##
==========================================
- Coverage   95.58%   95.57%   -0.02%     
==========================================
  Files         147      148       +1     
  Lines        6616     6666      +50     
  Branches     1891     1910      +19     
==========================================
+ Hits         6324     6371      +47     
- Misses        111      112       +1     
- Partials      181      183       +2

Impacted Files	Coverage Δ
packages/eslint-plugin/src/util/astUtils.ts	87.5% <ø> (ø)	⬆️
packages/eslint-plugin/src/rules/index.ts	100% <100%> (ø)	⬆️
packages/eslint-plugin/src/rules/comma-spacing.ts	93.87% <93.87%> (ø)

[bradzacher]

LGTM - thanks