feat: header append

Author: yossydev

examples/headers.ts

@@ -13,3 +13,7 @@ const headers2 = [
 const myHeaders2 = new Headers(headers2);
 console.log("myHeaders2", myHeaders2); // TODO Headers { 'Set-Cookie': 'greeting=hello, name=world' } but [object Object]
 console.log("myHeaders", myHeaders2.get("Set-Cookie")); // greeting=hellogreeting=hello,name=worldname=world
+
+const myAppendHeader = new Headers();
+myAppendHeader.append("Content-Type", "image/jpeg");
+console.log("myAppendHeader", myAppendHeader.get("Content-Type")); // 'image/jpeg'

runtime/src/ext/fetch/headers/mod.ts

@@ -15,9 +15,13 @@ class Headers {
 
   // https://fetch.spec.whatwg.org/#dom-headers-get
   get(name: string) {
-    // @ts-ignore
     return getHeader(this.headerList, name);
   }
+
+  // https://fetch.spec.whatwg.org/#dom-headers-append
+  append(name, value) {
+    return appendHeader(this, name, value);
+  }
 }
 
 function fillHeaders(headers: Headers, object) {