Add Option to Overwrite Kubernetes Schema

Add an option to overwrite the default Kubernetes schema URL with a
custom one, by setting a `YAMLLS_KUBERNETES_SCHEMA_URL` environment
variable.

See
- redhat-developer#998
- redhat-developer#824
- redhat-developer#841
- redhat-developer#962
- redhat-developer#1050

Main use case is to use
https://github.com/ricoberger/kubernetes-json-schema, which contains the
schema for Kubernetes and the CRDs I'm using.

Author: ricoberger

src/languageservice/utils/schemaUrls.ts

@@ -6,6 +6,7 @@ import { isBoolean } from './objects';
 import { isRelativePath, relativeToAbsolutePath } from './paths';
 
 export const KUBERNETES_SCHEMA_URL =
+  process.env.YAMLLS_KUBERNETES_SCHEMA_URL ||
   'https://raw.githubusercontent.com/yannh/kubernetes-json-schema/master/v1.32.1-standalone-strict/all.json';
 export const JSON_SCHEMASTORE_URL = 'https://www.schemastore.org/api/json/catalog.json';