feat(template) use the new default-run manifest field (#17)

templates/rust/Cargo.toml

@@ -7,6 +7,7 @@ license = ""
 repository = ""
 build = "build.rs"
 include = ["data"]
+default-run = "app"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html