feat: f32/f64 cargo features added

Signed-off-by: Stephen Waits <steve@waits.net>

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "vivaldi-nc"
-version = "0.5.1"
+version = "0.5.2"
 edition = "2021"
 authors = ["Stephen Waits <steve@waits.net>"]
 description = "Vivaldi network coordinates for fast, distributed latency estimates in multinode networks, with a clean and simple interface."
@@ -15,6 +15,11 @@ exclude = [
 	"examples/*",
 ]
 
+[features]
+default = ["f32"]
+f32 = []
+f64 = []
+
 [dev-dependencies]
 assert_approx_eq = "1.1.0"
 proptest = "1.0.0"