add support for function overloads (?)

[danielroe]

e.g.:

/**
 * @param path - The value provided
 */
export function someFunction (path: string): string

/**
 * @param factory - sample start
 * @param subpath - sub value
 */
export function someFunction (factory: () => any, subpath: string): string
export function someFunction (param1: string | (() => any), param2?: string): string {
  // implementation
}

[pi0]

We can (and should) support for overloads but it is beyond function only. Reference might also need overloads (like serverMiddleware can be arrray or object). For this we need an schema. I'm adding pending label to this issue since particularly function overloading is not a requirement now.