fix(types): top level declaration, closes #459 (#462)

Author: cristianireyes

types/index.d.ts

@@ -1,6 +1,6 @@
 import Vue, { VueConstructor, DirectiveOptions, PluginFunction } from 'vue';
 
-const vToolTip: PluginFunction<any>;
+declare const vToolTip: PluginFunction<any>;
 export default vToolTip;
 
 export const VPopover: VueConstructor<Vue>;