Sprinkle a few more deprecations

Author: armanbilge

src/main/scala/org/scalajs/dom/ext/Ajax.scala

@@ -15,7 +15,10 @@ import scala.scalajs.js.typedarray.TypedArrayBufferOps._
   */
 object Ajax {
 
-  /** Supported data formats for Ajax are implicitly converted to InputData */
+  /** Supported data formats for Ajax are implicitly converted to InputData
+    * @deprecated
+    *   use the `dom.fetch` API instead
+    */
   @js.native
   sealed trait InputData extends js.Any
 
@@ -45,31 +48,37 @@ object Ajax {
     }
   }
 
+  /** @deprecated use the `dom.fetch` API instead */
   def get(url: String, data: InputData = null, timeout: Int = 0, headers: Map[String, String] = Map.empty,
       withCredentials: Boolean = false, responseType: String = ""): Future[dom.XMLHttpRequest] = {
     apply("GET", url, data, timeout, headers, withCredentials, responseType)
   }
 
+  /** @deprecated use the `dom.fetch` API instead */
   def post(url: String, data: InputData = null, timeout: Int = 0, headers: Map[String, String] = Map.empty,
       withCredentials: Boolean = false, responseType: String = ""): Future[dom.XMLHttpRequest] = {
     apply("POST", url, data, timeout, headers, withCredentials, responseType)
   }
 
+  /** @deprecated use the `dom.fetch` API instead */
   def put(url: String, data: InputData = null, timeout: Int = 0, headers: Map[String, String] = Map.empty,
       withCredentials: Boolean = false, responseType: String = ""): Future[dom.XMLHttpRequest] = {
     apply("PUT", url, data, timeout, headers, withCredentials, responseType)
   }
 
+  /** @deprecated use the `dom.fetch` API instead */
   def patch(url: String, data: InputData = null, timeout: Int = 0, headers: Map[String, String] = Map.empty,
       withCredentials: Boolean = false, responseType: String = ""): Future[dom.XMLHttpRequest] = {
     apply("PATCH", url, data, timeout, headers, withCredentials, responseType)
   }
 
+  /** @deprecated use the `dom.fetch` API instead */
   def delete(url: String, data: InputData = null, timeout: Int = 0, headers: Map[String, String] = Map.empty,
       withCredentials: Boolean = false, responseType: String = ""): Future[dom.XMLHttpRequest] = {
     apply("DELETE", url, data, timeout, headers, withCredentials, responseType)
   }
 
+  /** @deprecated use the `dom.fetch` API instead */
   def apply(method: String, url: String, data: InputData, timeout: Int, headers: Map[String, String],
       withCredentials: Boolean, responseType: String): Future[dom.XMLHttpRequest] = {
     val req = new dom.XMLHttpRequest()