🤖 Merge PR DefinitelyTyped#71435 feat(css-tree): add lexer by @ryo-manba

Author: ryo-manba

types/css-tree/css-tree-tests.ts

@@ -749,3 +749,5 @@ lexer.match("foo", ast); // $ExpectType LexerMatchResult
 lexer.match("foo", "bar"); // $ExpectType LexerMatchResult
 lexer.match(syntax, ast); // $ExpectType LexerMatchResult
 lexer.match(syntax, "bar"); // $ExpectType LexerMatchResult
+
+csstree.lexer; // $ExpectType Lexer

types/css-tree/index.d.ts

@@ -907,6 +907,8 @@ export class Lexer {
     match(syntax: DSNode | string, value: CssNode | string): LexerMatchResult;
 }
 
+export const lexer: Lexer;
+
 export function fork(extension: {
     atrules?: Record<string, string> | undefined;
     properties?: Record<string, string> | undefined;