Implement editor.uploadFile syscall (#570)

* Implement editor.attachFile syscall

* Refactor attachFile to uploadFile

returns a promise with an UploadFile now

* Fix style

* Reject promise with errors

* Another code style fix

---------

Co-authored-by: prcrst <p-github@prcr.st>

plug-api/silverbullet-syscall/editor.ts

@@ -1,4 +1,5 @@
 import type { FilterOption } from "../../web/types.ts";
+import { UploadFile } from "../types.ts";
 import { syscall } from "./syscall.ts";
 
 export function getCurrentPage(): Promise<string> {
@@ -55,6 +56,10 @@ export function downloadFile(filename: string, dataUrl: string): Promise<void> {
   return syscall("editor.downloadFile", filename, dataUrl);
 }
 
+export function uploadFile(accept?: string, capture?: string): Promise<UploadFile> {
+  return syscall("editor.uploadFile", accept, capture);
+}
+
 export function flashNotification(
   message: string,
   type: "info" | "error" = "info",