Add a "pre" polyfill

This is always run, but only the full webcomponents polyfill, it's very
small and isn't intrusive. This introduces a layer of indirection so that,
if the full polyfill is loaded, its monkeypatched constructor will be called

src/cdp/domains/page.zig

@@ -284,6 +284,9 @@ pub fn pageCreated(bc: anytype, page: *Page) !void {
     if (bc.isolated_world) |*isolated_world| {
         // We need to recreate the isolated world context
         try isolated_world.createContext(page);
+
+        const polyfill = @import("../../browser/polyfill/polyfill.zig");
+        try polyfill.preload(bc.arena, &isolated_world.executor.js_context.?);
     }
 }