HTML sanitizer strips lang attributes

[artemist]

Steps to reproduce the problem

1. Switch post to HTML mode
2. Write post which includes han characters with multiple languages (e.g. <span lang="zh-Hans">北京</span><span lang="zh-Hant">【入】</span>. )
3. Attempt to view post in any way, e.g. via web interface, 3rd party client, etc.
   ...

Expected behaviour

Text renders using the langauages specified in the span tags: 北京【入】

Actual behaviour

Text renders using the post language: 北京【入】

Detailed description

Failing to pass langauge tags is a common rendering issue due to han unification.

Mastodon instance

social.mildlyfunctional.gay

Mastodon version

v4.4.0-alpha.2+glitch

Technical details