:autolink option adds non UTF-8 chars when email is next to Japanese text

[johnnyshields]

Tested on Ruby 3.0 with latest redcarpet master ref 50961ad (issue also present on latest release v3.5.1)

This code demonstrates the issue:

Redcarpet::Markdown.new(Redcarpet::Render::HTML, { autolink: true }).render('連絡先：test@test.com')
#=> "<p>連絡先\xEF\xBC<a href=\"mailto:%9Atest@test.com\">\x9Atest@test.com</a></p>\n"

Notice presence of non-UTF-8 chars \xEF\xBC and \x9A. When using in a Rails view, etc. you'll get:

ArgumentError - invalid byte sequence in UTF-8

As a workaround, adding a normal whitespace char just before the email address prevents the issue.