Added Wiki Link

Author: MiloTodt

lib/main-menu.js

@@ -384,6 +384,10 @@ const help = {
       label: 'Boostnote official site',
       click () { shell.openExternal('https://boostnote.io/') }
     },
+    {
+      label: 'Wiki',
+      click () { shell.openExternal('https://github.com/BoostIO/Boostnote/wiki') }
+    },
     {
       label: 'Issue Tracker',
       click () { shell.openExternal('https://github.com/BoostIO/Boostnote/issues') }