Use msgpack for API (#1176)

Cargo.lock

@@ -2078,10 +2078,12 @@ dependencies = [
  "rbx_xml",
  "reqwest",
  "ritz",
+ "rmp-serde",
  "roblox_install",
  "rojo-insta-ext",
  "semver",
  "serde",
+ "serde_bytes",
  "serde_json",
  "serde_yaml",
  "strum",
@@ -2222,6 +2224,16 @@ dependencies = [
  "serde_derive",
 ]
 
+[[package]]
+name = "serde_bytes"
+version = "0.11.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5d440709e79d88e51ac01c4b72fc6cb7314017bb7da9eeff678aa94c10e3ea8"
+dependencies = [
+ "serde",
+ "serde_core",
+]
+
 [[package]]
 name = "serde_cbor"
 version = "0.11.2"