feat(gnoweb): expose Render() link from directory view

[davd-gzl]

In the directory view (gno.land/pkg/gnoweb/components/views/directory.html), files and the README are listed and linkable, but there is no direct entry point to the realm's Render() output.

To reach the rendered realm from the directory view, users have to open a file first and then click the "Render" link at the top. There's no direct shortcut from the directory listing itself.

Expected: add a visible link/button to the realm's render view (e.g. next to the header or the README "Open" button) when the package is a realm.

Refs: gno.land/pkg/gnoweb/components/views/directory.html.

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Step by step:

• http://127.0.0.1:8888/r/gnoland/blog/ (Directory view)
• http://127.0.0.1:8888/r/gnoland/blog$source&file=admin.gno (File view)
• http://127.0.0.1:8888/r/gnoland/blog (Render view)