Don't try parsing non-markdown files (#152661)

This fixes our references and rename provider to not try parsing non-markdown files as if they were markdown

extensions/markdown-language-features/src/util/file.ts

@@ -4,7 +4,24 @@
  *--------------------------------------------------------------------------------------------*/
 
 import * as vscode from 'vscode';
+import * as URI from 'vscode-uri';
+
+const markdownFileExtensions = Object.freeze<string[]>([
+	'.md',
+	'.mkd',
+	'.mdwn',
+	'.mdown',
+	'.markdown',
+	'.markdn',
+	'.mdtxt',
+	'.mdtext',
+	'.workbook',
+]);
 
 export function isMarkdownFile(document: vscode.TextDocument) {
 	return document.languageId === 'markdown';
-}
+}
+
+export function looksLikeMarkdownPath(resolvedHrefPath: vscode.Uri) {
+	return markdownFileExtensions.includes(URI.Utils.extname(resolvedHrefPath).toLowerCase());
+}

extensions/markdown-language-features/src/util/schemes.ts

@@ -32,15 +32,3 @@ export function getUriForLinkWithKnownExternalScheme(link: string): vscode.Uri |
 export function isOfScheme(scheme: string, link: string): boolean {
 	return link.toLowerCase().startsWith(scheme);
 }
-
-export const MarkdownFileExtensions: readonly string[] = [
-	'.md',
-	'.mkd',
-	'.mdwn',
-	'.mdown',
-	'.markdown',
-	'.markdn',
-	'.mdtxt',
-	'.mdtext',
-	'.workbook',
-];