Move crates under a sub folder to clean up the code

crates/flatten-serde-json/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "flatten-serde-json"
+description = "Flatten serde-json objects like elastic search"
+readme = "README.md"
+publish = false
+
+version.workspace = true
+authors.workspace = true
+# description.workspace = true
+homepage.workspace = true
+# readme.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+serde_json = "1.0"
+
+[dev-dependencies]
+criterion = { version = "0.5.1", features = ["html_reports"] }
+
+[[bench]]
+name = "benchmarks"
+harness = false