Submit freedesktop.org shared-mime-info PR for Linux MIME recognition

[omscse]

Add .pweb / application/vnd.portableweb+zip to the freedesktop.org shared-mime-info database so Linux desktops (GNOME, KDE, etc.) recognise the format automatically.

Steps:

1. Fork https://gitlab.freedesktop.org/xdg/shared-mime-info
2. Add an entry to data/freedesktop.org.xml.in:

   <mime-type type="application/vnd.portableweb+zip">
     <comment>PortableWeb bundle</comment>
     <glob pattern="*.pweb"/>
     <magic priority="50">
       <match type="string" value="PK\003\004" offset="0"/>
     </magic>
   </mime-type>

3. Open a merge request

Improves file(1) detection and file manager integration on Linux.