Adding toWebviewResource api

For #76489

src/vs/workbench/api/common/shared/webview.ts

@@ -0,0 +1,24 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { URI } from 'vs/base/common/uri';
+import * as vscode from 'vscode';
+
+export interface WebviewInitData {
+	readonly webviewResourceRoot: string;
+	readonly webviewCspRule: string;
+}
+
+export function toWebviewResource(
+	initData: WebviewInitData,
+	resource: vscode.Uri
+): vscode.Uri {
+	const rootUri = URI.parse(initData.webviewResourceRoot);
+	return rootUri.with({
+		path: rootUri.path + resource.path,
+		query: resource.query,
+		fragment: resource.fragment,
+	});
+}