colocate css-parser benchmark file in src folder (tailwindlabs#13543)

Author: RobinMalfait

packages/tailwindcss/css-parser.bench.ts renamed to packages/tailwindcss/src/css-parser.bench.ts

@@ -1,8 +1,8 @@
 import { readFileSync } from 'node:fs'
 import { bench } from 'vitest'
-import * as CSS from './src/css-parser.ts'
+import * as CSS from './css-parser.ts'
 
-const currentFolder = new URL('.', import.meta.url).pathname
+const currentFolder = new URL('..', import.meta.url).pathname
 const cssFile = readFileSync(currentFolder + './preflight.css', 'utf-8')
 
 bench('css-parser on preflight.css', () => {