Consider enabling `explicit-module-boundary-types`

## Describe the feature

Explicit types for function return values and arguments makes it clear to any calling code what is the module boundary's input and output.

https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/explicit-module-boundary-types.md

This might be a big change for some of the projects that use this config, so it should be considered as breaking change.

## Motivation

It improves debugging and makes sure that returned types are correct.

## Related Issues

https://github.com/facebook/jest/pull/9539