separate spicetify menu items from spotify ones

📝 Provide a description of the new feature

for example:

• check through list of all li items
• pick out the one containing an svg with aria-label External link
• append vvMORUKtQKpQcpQ992bR classname to its button

alternatively:
or via some other method idk how menu items and context menus now work, potentially create a store of all menu items registered like we do with topbar buttons and if its the first one to be registered add a border to the bottom of it instead? that approach could also work for normal context menus that way!

➕ Additional Information

Start by locating how Spotify menu items and context menus are registered, then compare that with the existing topbar button registration approach mentioned in the issue. The issue suggests either identifying the item containing an SVG with aria-label "External link" and adding the vvMORUKtQKpQcpQ992bR class, or separating registered menu items with a bottom border. Done means Spicetify and Spotify menu items are visually distinct without breaking normal context menus.