Move crates under a sub folder to clean up the code

crates/flatten-serde-json/fuzz/fuzz_targets/flatten.rs

@@ -0,0 +1,12 @@
+#![no_main]
+use arbitrary_json::ArbitraryObject;
+use flatten_serde_json::flatten;
+use json_depth_checker::should_flatten_from_value;
+use libfuzzer_sys::fuzz_target;
+
+fuzz_target!(|object: ArbitraryObject| {
+    let object = flatten(&object);
+    if !object.is_empty() {
+        assert!(object.values().any(|value| !should_flatten_from_value(value)));
+    }
+});