Add 'allow' option to the no-relative-parent-imports rule or 'ignoreChildren' option to no-internal-modules rule.

Our use case is to have some util classes/functions in a folder on top and then always import using relative path. Eg.

src/
 utils/
   util1.js
 comp1/
   index.js
 comp2/
   index.js

From src/comp1/index.js i'd like to be able to import from ../utils/util1 but prohibit import from ../comp2

To achieve this, I see two options:

1. add 'allow' option to no-relative-parent-imports rule (in the same form as no-internal-modules 'allow'), eg.

"import/no-relative-parent-imports": [ "error", { "allow": ["**/src/utils/**"] } ]

2. add 'ignoreChildren' option to no-internal-modules to only inspect parent's internal modules, eg.

"import/no-internal-modules": [ "error", { "allow": ["**/src/utils/**"], "ignoreChildren": true  } ]

I'm willing to provide a PR to any of the rules.