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!

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