feat: add __performance

__performance/print_perf/src/main.rs

@@ -0,0 +1,34 @@
+use print_perf::*; 
+// or explicit print_perf::{perf, Perf};
+use std::time::Duration;
+use std::thread::sleep;
+
+fn add(a: i32, b: i32) -> i32 {
+    sleep(Duration::from_millis(100));
+    a + b
+}
+
+fn main() {
+    println!("main_1()");
+    main_1();
+    println!("main_2()");
+    main_2();
+}
+
+fn main_1() {
+    let add_p = perf!("add fn");
+    let result = add(4, 4);
+    add_p.end();
+    // ^-- prints: 0.100140446 (add fn) @ [src/main.rs:9]
+    assert_eq!(result, 8);
+}
+
+
+fn main_2() {
+    let p = perf!("add fn");
+    let _result = add(4, 4);
+    p.split("add");
+    let _div = _result / 2;
+    p.split("div");
+    p.end();
+}