Add docs from gofiber/fiber@3ab3d15

Author: github-actions[bot]

docs/core/api/client.md

@@ -268,10 +268,10 @@ agent.BodyStream(strings.NewReader("body=stream"), -1)
 
 ### JSON
 
-JSON sends a JSON request by setting the Content-Type header to `application/json`.
+JSON sends a JSON request by setting the Content-Type header to the `ctype` parameter. If no `ctype` is passed in, the header is set to `application/json`.
 
 ```go title="Signature"
-func (a *Agent) JSON(v interface{}) *Agent
+func (a *Agent) JSON(v interface{}, ctype ...string) *Agent
 ```
 
 ```go title="Example"

docs/core/api/ctx.md

@@ -797,7 +797,7 @@ app.Get("/", func(c *fiber.Ctx) error {
 Converts any **interface** or **string** to JSON using the [encoding/json](https://pkg.go.dev/encoding/json) package.
 
 :::info
-JSON also sets the content header to the `ctype` parameter. If no `ctype` is passed in, the header is set to **application/json**.
+JSON also sets the content header to the `ctype` parameter. If no `ctype` is passed in, the header is set to `application/json`.
 :::
 
 ```go title="Signature"