Publish to Open VSX Registry

[3w36zj6]

Since Visual Studio Marketplace cannot be used with forks of VS Code, it is necessary to publish the extension to the Open VSX Registry for the convenience of users.

Also, since the extension is already managed under the organization, I think it would be best to distribute it under the textlint namespace from the beginning.

https://github.com/eclipse/openvsx/wiki/Namespace-Access