Cache GeoJSON files

[ymhuang0808]

After downloading the shelter GeoJSON files, MAD will store the GeoJSON on app

[ymhuang0808]

After MAD App downloads shelter GeoJSON file, MAD App stores the GeoJSON file into local storage.
@bookjan , I think the shelter GeoJSON file should contain shelter version? It may help MAD update the latest shelter GeoJSON file.

[bookjan]

Let's go on Cache feature first.

[ymhuang0808]

No problem, Johnson~

[ymhuang0808]

According to the current coordinate, the MAD app will get the correct GeoJSON file/data from Interface server. However, firstly, we implement the cache functionality. ✌️