Check if element types of Promises contain a property when issuing a missing property error

[DanielRosenwasser]

function f(x: Promise<string>) {
  x.toLowerCase()
}

Expected: Property 'toLowerCase' does not exist on type 'Promise<string>'. Did you forget to await the 'Promise<string>'?

Actual: Property 'toLowerCase' does not exist on type 'Promise<string>'.

[mhegazy]

PRs welcomed. great first issue. will diffidently add value to our users.

[mhegazy]

The follow up to this issue is to add a quick fix to add the await keyword.

[akhomchenko]

I'll try to fix this.