Geocoding SDK (MAPCO-4537)

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 package.
If we create an SDK, we should also fetch the routes for the user.

TODO: add further information and a design.

首先明确 SDK 的设计，包括从公共 S3 bucket 启动时获取数据、每小时刷新表、纬度-经度转换以及路线获取。在定位实现入口之前，先审查 async-cache-dedupe 并定义 SDK 的验收标准；issue 的 TODO 表明设计尚未确定。