@directive and @@directive improvements

[CarlOlson]

Directives are a part of React and used by the React compiler. Frameworks like NextJs have started to rely on these heavily. ReScript should improve its support in order to take advantages of these features.

Suggested Changes:

1. Always output value given to @@directive as a string. Example: @@directive("use client"), not @@directive("'use client'")

   Currently @@directive can generate invalid JS:

   @@directive("use client")

   // output
   use client
   
   // should be
   "use client"

   Directives are always strings, so we shouldn't need to add internal quotes.

2. Support @directive for react components and functions

   @rescript.component @directive("use client")
   let make = () => {
     <div />
   }
   
   @directive("use server")
   let submit = (input: FormAction.t) => {
     await input->save
   }

[fhammerschmidt]

2. is supported but you need to put the directive before the parameters, not before the binding:

@rescript.component
let make =
  @directive("use client")
  () => {
    <div />
  }

let submit =
  @directive("use server")
  async (input: string) => {
    await input->save
  }