Unknown schemes don’t work as link

Hello!

Sometimes a webmaster needs to create a linked QR code on scheme, which are not well-known, but are worked out by the browser software. For example, “lightning:” (lightning network of bitcoin), “lnurlw://”, etc. As I understood by trial, your plugin only creates a link to the QR code if the scheme type is known to it (http, https, mailto) and does not create a link if the scheme is not known to it. This is wrong. Let the webmaster do this and include urls of all types.