Publish on open-vsx

Hi, @ryuta46! I've got an [extension](https://github.com/br4ch1st0chr0n3/vscode-purs-keybindings) for PureScript that depends on yours awesome `multi-command`, and I'd like to use it via [open-vsx](https://open-vsx.org/) in VSCodium. For now, I [published](https://open-vsx.org/extension/ryuta46/multi-command) your extension just to have it there. However, could you please publish it officially?