Alternative scheme support for the markdown URL

[oooo-ps]

Current Behavior

I have following issue with Markdown parser:

[alt](gemini://site.com)

• where gemini is the alternative protocol; the URL is valid anyway, but could not be parsed with engine (v2 beta)

Steps to Reproduce

Just text entry in the new message form

Expected Behavior

It should be clickable, but I see the plain markdown text like on example above

Screenshots

No response

Environment

• Flarum version: v2 beta (repository)
• Webserver: nginx
• Hosting environment: vps
• PHP version: 8.2

Output of php flarum info

php flarum info
Flarum core: 2.0.0-beta.3
PHP version: 8.2.29
SQLite version: 3.40.1
Loaded extensions: Core, date, libxml, openssl, pcre, zlib, filter, hash, json, pcntl, random, Reflection, SPL, session, standard, sodium, PDO, xml, apcu, calendar, ctype, curl, dom, mbstring, FFI, fileinfo, ftp, gd, gettext, iconv, intl, exif, pdo_sqlite, Phar, posix, readline, shmop, SimpleXML, sockets, sqlite3, sysvmsg, sysvsem, sysvshm, tokenizer, xmlreader, xmlwriter, xsl, zip, Zend OPcache
+----------------------+---------+--------+
| Flarum Extensions    |         |        |
+----------------------+---------+--------+
| ID                   | Version | Commit |
+----------------------+---------+--------+
| flarum-tags          | 2.x-dev |        |
| flarum-suspend       | 2.x-dev |        |
| flarum-subscriptions | 2.x-dev |        |
| flarum-sticky        | 2.x-dev |        |
| flarum-mentions      | 2.x-dev |        |
| flarum-markdown      | 2.x-dev |        |
| flarum-lock          | 2.x-dev |        |
| flarum-likes         | 2.x-dev |        |
| flarum-lang-english  | 2.x-dev |        |
| flarum-flags         | 2.x-dev |        |
+----------------------+---------+--------+
Base URL: 
Installation path: /var/www/flarum
Queue driver: sync
Session driver: file
Mail driver: mail
Debug mode: off

Possible Solution

No response

Additional Context

No response

[RokeJulianLockhart]

If non-HTTP schemas are permitted, that'll be an edge over most competition. However, although any decent browser always warns before invoking such a URI in its associated consumer, reasons exist that most forums don't permit these.