fix: parserOptions, rules default values for ESLint 6

[wheeler]

Problem

When trying to use jest-runner-eslint on a project being upgraded to ESLint 6 there are the following errors:

ESLint configuration in CLIOptions is invalid:
    - Property "parserOptions" is the wrong type (expected object but got `null`).
    - Property "rules" is the wrong type (expected object but got `null`).

Setup

I "use ESLint 6" by forcing the version using the following in my package.json

  "resolutions": { "eslint": "6.4.0" },

Cause

ESLint 6 introduces type checks on the config.
See ~ PR: eslint/eslint#11546 || Commit: eslint/eslint@6ae21a4

Two default values set in normalizeConfig.js are not compatible.

• config.parserOptions is typed as an object so null is not valid.
  https://github.com/eslint/eslint/blob/2e202ca2228846e6226aa8dd99c614d572fb86a8/lib/shared/types.js#L22

• config.rules is typed as a Record so null is not valid.
  https://github.com/eslint/eslint/blob/2e202ca2228846e6226aa8dd99c614d572fb86a8/lib/shared/types.js#L41

Fix

Change the default values for these two configurations from null to {} in normalizeConfig.js.

Using this change jest-runner-eslint + ESlint 6 runs normally for my project. I also tested with this change but back on ESLint 5 and that continues to work.

This is not intended to fully support ESLint 6 but step in the right direction.

[ljharb]

This seems like an overlap of #70.

[wheeler]

@ljharb I agree there is overlap. #70 fixes one of these fields under the umbrella of allowing ESLint 6. This fixes two. This PR does not contain the assertion that ESLint 6 is fully supported - but it does not have any impact on ESLint 5. If this were merged and #70 were rebased that would then contain only the package.json changes allowing ESLint 6 (and possibly be closer to passing).

Edit: I see now that #70 mentions parserOptions but does not fix it. Please let me know if you would like this PR changed to have a different scope or if there is some way I could contribute to moving #70 forward.

[ljharb]

There's no value imo in adding anything less than full support for ES6 (which is sorely needed)

[wheeler]

OK, closing.

[wheeler]

@ljharb more complete version here -> #77