fix(typescript): enable importFileExtension option

This commit updates the TypeScript generator options to include
importFileExtension. This is done in order to support ESM in
the JavaScript client, as ESM requires explicit extensions.

Refs: kubernetes-client/javascript#2062

Author: cjihrig

openapi/typescript.xml

@@ -35,6 +35,7 @@
                                 <npmName>kubernetes-client-typescript</npmName>
                                 <npmVersion>${generator.client.version}</npmVersion>
                                 <modelPropertyNaming>original</modelPropertyNaming>
+                                <importFileExtension>.js</importFileExtension>
                             </configOptions>
                             <typeMappings>int-or-string=IntOrString,date-time-micro=V1MicroTime</typeMappings>
                         </configuration>