(fix) add eslint-config-grumbler to resolve plugin install issue

[imbrian]

Fixes issue installing a few eslint-plugin-* packages provided by @krakenjs/eslint-config-grumbler via @krakenjs/grumbler-scripts, where npm is no longer flattening these to node_modules/eslint-plugin-*. eslint then cannot find the plugin. See here.

I did observe that removing mocketeer as a devDependency appears to also resolve this, but this package is used in checkout-components, which is experiencing the same issue.

Possible alternatives:

• specify all eslint-plugin-* packages from grumbler-scripts
• determine dependency causing this and use npm overrides to pin version
• remove mocketeer as dependency
• use of lockfile to prevent/identify unexpected graph changes due to transitive dependency updates (might not solve the underlying issue, but would prevent the unexpected change).

[jshawl]

For posterity: It's not clear to me why this is failing all of a sudden:

• @krakenjs/grumbler-scripts has not been updated (https://github.com/krakenjs/grumbler-scripts/blame/de4b7a3490bff44cc9ebb7dc88eea87f64b96a36/packages/grumbler-scripts/package.json#L3)
• eslint-plugin-flowtype has not been updated (https://www.npmjs.com/package/eslint-plugin-flowtype)
  🤔
  but without the lockfile I can't think of a way to debug the failure further, so I like your solution!

[imbrian]

For posterity: It's not clear to me why this is failing all of a sudden:

• @krakenjs/grumbler-scripts has not been updated (https://github.com/krakenjs/grumbler-scripts/blame/de4b7a3490bff44cc9ebb7dc88eea87f64b96a36/packages/grumbler-scripts/package.json#L3)
• eslint-plugin-flowtype has not been updated (https://www.npmjs.com/package/eslint-plugin-flowtype)
  🤔
  but without the lockfile I can't think of a way to debug the failure further, so I like your solution!

agree. It has to be another transitive dependency that updated, and npm now decides the ideal graph no longer flattens those. mocketeer does specify eslint 5 as a dependency, which I why I looked into that, but still not following the magic behind why that's causing this. That version is not flattened; eslint 8 is at the root.