Mark some constants are readonly

extensions/markdown/src/documentLinkProvider.ts

@@ -41,9 +41,9 @@ function matchAll(pattern: RegExp, text: string): Array<RegExpMatchArray> {
 }
 
 export default class LinkProvider implements vscode.DocumentLinkProvider {
-	private linkPattern = /(\[[^\]]*\]\(\s*?)(((((?=.*\)\)+)|(?=.*\)\]+))[^\s\)]+?)|([^\s]+)))\)/g;
-	private referenceLinkPattern = /(\[([^\]]+)\]\[\s*?)([^\s\]]*?)\]/g;
-	private definitionPattern = /^([\t ]*\[([^\]]+)\]:\s*)(\S+)/gm;
+	private readonly linkPattern = /(\[[^\]]*\]\(\s*?)(((((?=.*\)\)+)|(?=.*\)\]+))[^\s\)]+?)|([^\s]+)))\)/g;
+	private readonly referenceLinkPattern = /(\[([^\]]+)\]\[\s*?)([^\s\]]*?)\]/g;
+	private readonly definitionPattern = /^([\t ]*\[([^\]]+)\]:\s*)(\S+)/gm;
 
 	public provideDocumentLinks(
 		document: vscode.TextDocument,