chore(cli): add comments on app template Cargo.toml (#3441)

tooling/cli/templates/app/src-tauri/Cargo.crate-manifest

@@ -20,5 +20,9 @@ serde = { version = "1.0", features = ["derive"] }
 tauri = {{{  tauri_dep  }}}
 
 [features]
+# by default Tauri runs in production mode
+# when `tauri dev` runs it is executed with `cargo run --no-default-features` if `devPath` is an URL
 default = [ "custom-protocol" ]
+# this feature is used on production builds and when `devPath` points to the filesystem
+# DO NOT remove this
 custom-protocol = [ "tauri/custom-protocol" ]