Introduce HTTP API for plugins (#5383)

docs/chatterino.d.ts

@@ -32,6 +32,8 @@ declare module c2 {
     is_valid(): boolean;
   }
 
+  interface ISharedResource {}
+
   class RoomModes {
     unique_chat: boolean;
     subscriber_only: boolean;
@@ -69,6 +71,36 @@ declare module c2 {
     static by_twitch_id(id: string): null | Channel;
   }
 
+  enum HTTPMethod {
+    Get,
+    Post,
+    Put,
+    Delete,
+    Patch,
+  }
+
+  class HTTPResponse implements ISharedResource {
+    data(): string;
+    status(): number | null;
+    error(): string;
+  }
+
+  type HTTPCallback = (res: HTTPResponse) => void;
+  class HTTPRequest implements ISharedResource {
+    on_success(callback: HTTPCallback): void;
+    on_error(callback: HTTPCallback): void;
+    finally(callback: () => void): void;
+
+    set_timeout(millis: number): void;
+    set_payload(data: string): void;
+    set_header(name: string, value: string): void;
+
+    execute(): void;
+
+    // might error
+    static create(method: HTTPMethod, url: string): HTTPRequest;
+  }
+
   function log(level: LogLevel, ...data: any[]): void;
   function register_command(
     name: String,