[no-restricted-paths] Add options to ignore certain import kinds

[RebeccaStevens]

This adds a new option called "allowedImportKinds" to the rule no-restricted-paths.
This option defaults to an empty array and can be set to an array of strings.

This option allows imports of the specified kind(s) to be ignore by this rule.

Example use:

{
  // Allow type imports.
  "allowedImportKinds": ["type"],
  "zones": [ {
    "target": "./tests/files/restricted-paths/server/one",
    "from": "./tests/files/restricted-paths/server",
    // Override above `allowedImportKinds`, don't make an exception for any import kinds.
    "allowedImportKinds": [],
  } ]
}

[coveralls]

Coverage increased (+0.005%) to 97.911% when pulling 7e9d9a4 on RebeccaStevens:no-restricted-paths/allowed-import-kinds into fef718c on benmosher:master.

[RebeccaStevens]

@ljharb

I'm not sure if we need an enum - will there ever be another kind of import that's not value or type?

In this PR I haven't enforced the option being an enum, any strings can be given. With regard to whether there will be any other kinda of import, most likely not - but it's probably best to keep things flexible just in case.

[ljharb]

LGTM pending schema change.

[ljharb]

i do think we should restrict this for now to known import types. we can extend it in the future if needed, but we can't lock it down so easily.