Add telemtry property for local TS version

We are interested in understanding which TS versions user have enabled in their workspaces, and how widely these diverge from these the workspace version

extensions/typescript-language-features/src/typescriptServiceClient.ts

@@ -245,7 +245,7 @@ export default class TypeScriptServiceClient extends Disposable implements IType
 		this.logger.error(message, data);
 	}
 
-	private logTelemetry(eventName: string, properties?: { [prop: string]: string }) {
+	private logTelemetry(eventName: string, properties?: { readonly [prop: string]: string }) {
 		this.telemetryReporter.logTelemetry(eventName, properties);
 	}
 
@@ -287,7 +287,6 @@ export default class TypeScriptServiceClient extends Disposable implements IType
 
 		const apiVersion = this.versionPicker.currentVersion.apiVersion || API.defaultVersion;
 		this.onDidChangeTypeScriptVersion(currentVersion);
-
 		let mytoken = ++this.token;
 		const handle = this.typescriptServerSpawner.spawn(currentVersion, this.configuration, this.pluginManager);
 		this.serverState = new ServerState.Running(handle, apiVersion, undefined, true);
@@ -297,10 +296,13 @@ export default class TypeScriptServiceClient extends Disposable implements IType
 			"tsserver.spawned" : {
 				"${include}": [
 					"${TypeScriptCommonProperties}"
-				]
+				],
+				"localTypeScriptVersion":  { "classification": "SystemMetaData", "purpose": "FeatureInsight" }
 			}
 		*/
-		this.logTelemetry('tsserver.spawned');
+		this.logTelemetry('tsserver.spawned', {
+			localTypeScriptVersion: this.versionProvider.localVersion ? this.versionProvider.localVersion.versionString : '',
+		});
 
 		handle.onError((err: Error) => {
 			if (this.token !== mytoken) {

extensions/typescript-language-features/src/utils/telemetry.ts

@@ -14,7 +14,7 @@ interface PackageInfo {
 }
 
 export default interface TelemetryReporter {
-	logTelemetry(eventName: string, properties?: { [prop: string]: string }): void;
+	logTelemetry(eventName: string, properties?: { readonly [prop: string]: string }): void;
 
 	dispose(): void;
 }