add doc

README.md

@@ -1,2 +1,33 @@
 # axum-valid
 
+The Valid crate provides a `Valid` type that can be used in combination with `Json`, `Path`, `Query`, and `Form` types to validate the entities that implement the `Validate` trait.
+
+## Usage
+
+```rust
+use validator::Validate;
+use serde::Deserialize;
+
+#[derive(Debug, Validate, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct Pager {
+    #[validate(range(min = 1, max = 50))]
+    page_size: usize,
+    #[validate(range(min = 1))]
+    page_no: usize,
+}
+
+pub async fn get_page_by_query(
+    Valid(Query(pager)): Valid<Query<Pager>>,
+) {
+    assert!((1..=50).contains(pager.page_size));
+    assert!((1..).contains(pager.page_no));
+}
+
+pub async fn get_page_by_json(
+    Valid(Json(pager)): Valid<Json<Pager>>,
+) {
+    assert!((1..=50).contains(pager.page_size));
+    assert!((1..).contains(pager.page_no));
+}
+```