Add placeholder --run-server support.

This allows the program to run as a web server,
which will eventually be able to return
mushroom models.

src/args.rs

@@ -8,6 +8,10 @@ pub struct Args {
     #[arg(long, default_value = "mesh.stl")]
     pub output: String,
 
+    /// Shape of the cap.
+    #[arg(long, default_value_t = false)]
+    pub run_server: bool,
+
     /// Height of total mushroom in millimeters.
     #[arg(long, default_value_t = 100)]
     pub height: u32,