AWS::ApiGateway::Stage MethodSettings ResourcePath must start with a / #190

[benbridts]

cfn-lint version: (cfn-lint --version) 0.53.0

Description of issue.

When specifying a ResourcePath, there are complicated rules (https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-apitgateway-stage-methodsetting.html#cfn-apigateway-stage-methodsetting-resourcepath). One thing that is certain, is that it has to start with a /. The current Spec file, does not have any validation on that:

"ResourcePath": {
    "description": "...",
    "type": "string"
},

It would be nice if writing ResourcePath: * would throw an error, so that it's more likely that people write ResourcePath: /*. Ideally the full set of rules would be encoded in the spec.