Add max_warnings config option to `.flowconfig` file

[NameFILIP]

Proposal

There is currently a way to pass a --max-warnings 0 argument to the flow-cli, but it is not possible to configure it in the .flowconfig file. I propose adding a max_warnings config option.

Use case

I would like to keep the output of flow clean with 0 warnings and 0 errors. Currently, the CI does not fail on Warnings, so from time to time some warnings slip into the codebase. My current repository contains multiple services, where each service can call flow in their scripts. Adding a CLI argument will need to be repeated in multiple places in this case. All projects share a single .flowconfig file, so it would be great if the option can be configured in it.

See related issues:

• Exit as failure if warnings are present? #5009
• Docs say Unused Suppression is an error; Changelog says warning #5612 (comment) (an alternative approach to elevate "Unused suppression comment." warnings to errors)