Support multiple icon libraries

[julians300]

Right now the side nav menu only supports Feather icons. It would be nice to be able to plug in another (or any) icon library to be used in the nav.

[thebradisrad]

You can plug any icon library into the menu. Current it uses Feather icons. Look for the Feather icons in the NavSingleItem.js and NavDropDownItem.js and replace it with another library. You may need to adjust some code, but that's where you can make changes to icons.