refactor: pull things into own files, have a library

src/branding.rs

@@ -0,0 +1,8 @@
+pub fn startup_msg() {
+    let name = env!("CARGO_PKG_NAME");
+    let version = env!("CARGO_PKG_VERSION");
+    let authors = env!("CARGO_PKG_AUTHORS");
+
+    println!("{name} v{version} started.",);
+    println!("Copyright 2025 {authors}. All rights reserved.")
+}