Add typings

[matthieusieben]

I am currently using the following to type @hapi/vise. It would be nice if this module exported its own types. I d'ont have the time or resources to make a PR. Sorry about that.

// types.d.ts

declare module '@hapi/vise' {
  export class Vise {
    readonly length: number
    push(bhunk: Buffer): void
    readUInt8(pos: number): undefined | number
    at(pos: number): undefined | number
    chunks(): Buffer[]
    shift(length: number): Buffer[]
    startsWith(value: Buffer, pos?: number, length?: number): boolean
  }
}