Update Cargo badges and categories.

build/rapier2d/Cargo.toml

@@ -7,10 +7,14 @@ documentation = "http://docs.rs/rapier2d"
 homepage = "http://rapier.rs"
 repository = "https://github.com/dimforge/rapier"
 readme = "README.md"
+categories = [ "science", "game-development", "mathematics", "simulation", "wasm"]
 keywords = [ "physics", "dynamics", "rigid", "real-time", "joints" ]
 license = "Apache-2.0"
 edition = "2018"
 
+[badges]
+maintenance = { status = "actively-developed" }
+
 [features]
 default = [ "dim2", "f32" ]
 dim2    = [ ]