chore: example and readme

examples/log.rs

@@ -2,5 +2,17 @@
 
 // cargo run --example log
 fn main() {
+    std::env::set_var("LOGGER_LEVEL", "*");
+    println!(r##"env LOGGER_LEVEL set to:
+debug or *
+info or ? -- default
+ok or #
+warn or !
+error or ^"##);
+
+    debugging!("Hello {}", "world!");
     information!("Hello {}", "world!");
+    success!("Hello {}", "world!");
+    warning!("Hello {}", "world!");
+    failure!("Hello {}", "world!");
 }