Bump league/commonmark in /dokuwiki/lib/plugins/commonmark

Bumps [league/commonmark](https://github.com/thephpleague/commonmark) from 2.6.0 to 2.8.2.
- [Release notes](https://github.com/thephpleague/commonmark/releases)
- [Changelog](https://github.com/thephpleague/commonmark/blob/2.8/CHANGELOG.md)
- [Commits](thephpleague/commonmark@2.6.0...2.8.2)

---
updated-dependencies:
- dependency-name: league/commonmark
  dependency-version: 2.8.2
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

dokuwiki/lib/plugins/commonmark/composer.json

@@ -24,7 +24,7 @@
         }
     },
     "require": {
-        "league/commonmark": "2.6.*",
+        "league/commonmark": "2.8.*",
         "symfony/yaml": "4.*"
     },
     "config": {