test: add assets for performance test

- add tailwindcss and bootstrap file for performance test

Author: Ffloriel

packages/postcss-purgecss/package-lock.json

@@ -9,10 +9,7 @@ describe("performance", () => {
         // files in __tests__/test_examples, including tailwind.css, which is
         // a whopping 908KB of CSS before purging.
         content: ["./packages/purgecss/node_modules/**/*.js"],
-        css: [
-          "./packages/purgecss/__tests__/test_examples/*/*.css",
-          "./packages/purgecss/node_modules/tailwindcss/dist/tailwind.css",
-        ],
+        css: ["./packages/purgecss/__tests__/test_examples/*/*.css"],
       })
       .then((results) => {
         expect(results.length).toBeGreaterThanOrEqual(1);