add async versions of callback methods

[david-morris]

Async is often an easier to use abstraction for delayed computation than callbacks.

As a result, I've been writing code like this:

  const info = await new Promise<GetInfoCallbackResult>((resolve, reject) => {
    tiles.getInfo((error, info) => {
      if (error) {
        // eslint-disable-next-line no-console
        console.log(
          "failed to get tiles: ",
          TILES_PATH,
          " from ",
          process.cwd()
        )

        reject(error)
      } else {
        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
        resolve(info!)
      }
    })
  })

It would be nice if that became something like tiles.agetInfo(...).

It's also useful to await the constructor making things ready:

const TILES_OBJECT_PROMISE_CACHE = new Map<string, Promise<MBTiles>>()

export const getTileObject = async (uri: string): Promise<MBTiles> => {
  const cached = TILES_OBJECT_PROMISE_CACHE.get(uri)
  if (cached) return await cached
  const tilesObjectPromise = new Promise<MBTiles>((resolve, reject) => {
    const mbtiles = new MBTiles(uri, error => {
      if (error) {
        reject(error)
      } else {
        resolve(mbtiles)
      }
    })
  })
  TILES_OBJECT_PROMISE_CACHE.set(uri, tilesObjectPromise)
  return await tilesObjectPromise
}

It would be neat if the part where you get a promise was something like MBtiles.ABuildMBTiles(...).