Add science::geo category (#23)

- [x] I agree to follow the project's [code of
conduct](https://github.com/georust/geo/blob/master/CODE_OF_CONDUCT.md).
~- [ ] I added an entry to `CHANGES.md` if knowledge of this change
could be valuable to users.~
---

Fixes #21

Author: nyurik

Cargo.toml

@@ -13,6 +13,7 @@ homepage = "https://github.com/georust/tilejson"
 repository = "https://github.com/georust/tilejson"
 readme = "README.md"
 keywords = ["maplibre", "mapbox", "tilejson", "serde"]
+categories = ["science::geo"]
 
 [dependencies]
 serde = { version = "1", features = ["derive"] }