feat: added examples

examples/prefixed.rs

@@ -0,0 +1,16 @@
+use envkit::EnvLoader;
+
+fn main() -> Result<(), envkit::error::EnvError> {
+    let loader = EnvLoader;
+    let app = loader.with_prefix("APP_");
+
+    let host: String = app.get("HOST")?;
+    let port: u16 = app.get_or("PORT", 8080);
+    let enabled: bool = app.get_or("ENABLED", false);
+
+    println!("host={host}");
+    println!("port={port}");
+    println!("enabled={enabled}");
+
+    Ok(())
+}