Javascript client code generator

[pierremrtn]

Add support for generating Javascript client

[MrAlek]

Or rather Typescript. A simple Interface would suffice and would be way easier compared to the current Dart implementation.

Example:

export interface User {
  firstName: string
  lastName: string
  email?: string
}

Caveats are with types for set/update where there for instance is FieldValue.serverTimestamp() and FieldValue.arrayUnion() which would force to have a separate interface input interfaces.

Example:

export interface UserInput {
  firstName: string
  lastName: string
  email?: string
  friends: FieldValue
  lastUpdatedAt: FieldValue
}

export interface User extends UserInput {
  friends: DocumentReference<User>[]
  lastUpdatedAt: Timestamp
}

[pierremrtn]

Ideally I would like to support both.
It's been years since I've almost didn't write any JS beyond simple functions, so I'll need a refresher before working on this. I'll align as much as possible on real-world clients code available publicly or other generators if any.
I've heard some people are using the Zod parser, which might be an interesting option.

Right now I'm finalizing #6, which involves heavy underlying data structure changes. I'll get back to working on generators once it's done.