[Polyfill > Inject] Simplify by just making js files instead of dirs

scripts/injectPolyfills.js

@@ -1,4 +1,4 @@
-const { readdirSync, mkdirSync, copyFileSync } = require('fs');
+const { readdirSync, copyFileSync } = require('fs');
 const { join } = require('path');
 
 const rootDir = join(__dirname, '..');
@@ -8,11 +8,5 @@ for (const file of readdirSync(polyfillsDir)) {
   const [ name ] = file.split('.');
   const jsPath = join(polyfillsDir, file);
 
-  const moduleDir = join(rootDir, 'src', 'node_modules', name);
-
-  try {
-    mkdirSync(moduleDir);
-  } catch (e) {}
-
-  copyFileSync(jsPath, join(moduleDir, 'index.js'));
+  copyFileSync(jsPath, join(rootDir, 'src', 'node_modules', name + '.js'));
 }