actix-multipart: Feature: Add typed multipart form extractor (#2883)

Co-authored-by: Rob Ede <robjtede@icloud.com>

actix-multipart-derive/tests/trybuild/all-required.rs

@@ -0,0 +1,19 @@
+use actix_web::{web, App, Responder};
+
+use actix_multipart::form::{tempfile::TempFile, text::Text, MultipartForm};
+
+#[derive(Debug, MultipartForm)]
+struct ImageUpload {
+    description: Text<String>,
+    timestamp: Text<i64>,
+    image: TempFile,
+}
+
+async fn handler(_form: MultipartForm<ImageUpload>) -> impl Responder {
+    "Hello World!"
+}
+
+#[actix_web::main]
+async fn main() {
+    App::new().default_service(web::to(handler));
+}