feat: enable alternative config formats

[marionebl]

• use cosmiconfig for config in package.json and .commitlintrc support
• update ava
• adapt various t.throws tests

includes #83

[marionebl]

Published with v4.0.0 🚀

[Mouvedia]

You forgot to update the README.
https://github.com/conventional-changelog/commitlint/blob/master/README.md#config

[escapedcat]

@Mouvedia this was just merged: #2698
If you want to you can create a PR for the docs.

[songhn233]

@Mouvedia you can update for commitlintrc.ts and commitlintrc.yaml

[Mouvedia]

@songhn233 my point is .commitlintrc is perfectly compatible but missing from the list on the README.

[escapedcat]

@Mouvedia got it. If you have time, please create a PR to update the docs:

• https://github.com/conventional-changelog/commitlint/blob/master/README.md#config
• https://github.com/conventional-changelog/commitlint/blob/master/docs/guides-local-setup.md#install-commitlint

Thanks!