Support markdown2 2.4.10, 2.4.8- and exclude 2.4.9 Handle these changes to markdown2 version 2.4.9 broke links like (issue1)[issue1]: raise error if used Version 2.4.10 changed how filtering of schemes is done: adapt to new method Mail url's in markdown are formatted [label](mailto:user@something.com). The markdown format wrapper uses the plain text formatter to turn issue1 and user@something.com into markdown formatted strings to be htmlized by the markdown formatters. However when the plain text formatter saw (mailto:user@something.com) it made it (mailto:<user@something.com>). This is broken as the enamil address shouldn't have the angle brackets. By modifying the email pattern to include an optional mailto:, all three markdown formatters do the right thing and I don't end up with href="<user@something.com>" in the link.

--- a/CHANGES.txt	Sun Jul 23 16:11:23 2023 -0400
+++ b/CHANGES.txt	Sun Jul 23 16:50:35 2023 -0400
@@ -22,6 +22,9 @@
 - issue2551184 - improve i18n handling. Patch to test to make sure it
   uses the test tracker's locale files and not other locale
   files. (Marcus Priesch)
+- issue2551283 - fail if version 2.4.9 of markdown2 is used, it's
+  broken. Support version 2.4.10 with its new schema filtering
+  method and 2.4.8 and earlier. (John Rouillard)
 
 Features: