feat: add sincere

sincere/src/main.rs

@@ -0,0 +1,11 @@
+use sincere::App;
+
+fn main() {
+    let mut app = App::new();
+
+    app.get("/", |context| {
+        context.response.from_text("Hello world!").unwrap();
+    });
+
+    app.run("127.0.0.1:8000", 20).unwrap();
+}