Handle normalized windows paths in resource map

Fixes #86433

During path normalization, we convert `\` in windows paths to  `/`. This causes the isWindowsPath check to fail

I think it is generally safe to assume that file paths that start with a drive letter and then any type of slash should be treated as windows paths

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

@@ -101,5 +101,5 @@ export class ResourceMap<T> {
 }
 
 export function isWindowsPath(path: string): boolean {
-	return /^[a-zA-Z]:\\/.test(path);
+	return /^[a-zA-Z]:[\/\\]/.test(path);
 }