chore: updated notify types to match from IBrowserSyncOptions

[bgturner]

I was using BrowserSync within a different package and noticed that the types for the notify indicate that it's only a boolean:

But it looks like the IBrowserSyncOptions interface has the notify key accepting a CSS styles object or array of CSS style rules.

I'm not as familiar with this project, so I just copied the type definition, but when I run a diff between the InitOptions and IBrowserSyncOptions, it looks like they're mostly the same except for InitOptions having:

 userPlugins: any[]; session: number; 

Should the types between these two things the same, or should we consider importing and extending IBrowserSyncOptions?