Deprecated addWikiText() causes issue MediaWiki 1.32+

[DigiEggz]

When visiting the Special:LiteSpeedCache page to enable the plugin for the first time, the script breaks with the following error: /index.php/Special:LiteSpeedCache Error from line 131 of */extensions/LiteSpeedCache/SpecialLiteSpeedCache.php: Call to undefined method OutputPage::addWikiText()

A condtional needs to be added to that section to check if "addWikiTextAsInterface" exists, and then to use that instead of addWikiText(). Here's an example of the fix: https://phabricator.wikimedia.org/rEPFM59c1d49f8d43af087eed9d3868576155b91e8125