Geocoding SDK (MAPCO-4537)

まだ誰も着手していません。

Recently, users have reached out to us asking to be able, in their front-end applications, to show which control tile the user's mouse is on. This is essentially a simple Latitude-Longitude to Control Tile conversion.
Obviously, we can't handle so many conversion requests. But, we can't also send them conversion table that might change from time to time.
That's why, we want to build an SDK. On SDK's startup, It will pull locally the conversion table from a public S3 bucket. From time to time, it will refresh the table (We can start in every one hour). We should use [https://github.com/mcollina/async-cache-dedupe](`async-cache-dedupe`) package.
If we create an SDK, we should also fetch the routes for the user.

TODO: add further information and a design.

まず、公開 S3 バケットからの起動時の fetch、テーブルの毎時更新、緯度・経度の変換、ルートの fetch を含め、SDK の設計を明確にします。実装のエントリーポイントを探す前に async-cache-dedupe を確認し、SDK の受け入れ基準を定義してください。issue の TODO は、設計がまだ固まっていないことを示しています。

索引モデルが issue の本文から書いたものです。