LibWeb: Implement multiple import map support

Author: https://github.com/shannonbooth
Commit: ac6fe2e211
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2824
Reviewed-by: https://github.com/Lubrsi ✅

Tests/LibWeb/Text/input/HTML/import-maps-2.js

@@ -0,0 +1,3 @@
+export function main() {
+    println("(2) hello, friends!");
+}