Upload file command with copy/paste logic (#571)

Upload: File command

Co-authored-by: prcrst <p-github@prcr.st>
Co-authored-by: Zef Hemel <zef@zef.me>

web/syscalls/editor.ts

@@ -88,6 +88,7 @@ export function editorSyscalls(editor: Client): SysCallMapping {
               if (evt.target?.readyState == FileReader.DONE) {
                 resolve({
                   name: file.name,
+                  contentType: file.type,
                   content: new Uint8Array(await file.arrayBuffer()),
                 });
               }