Replace unmaintained `html-to-text` dependency

[baraknaveh]

@react-email/render depends on html-to-text for generating plain text versions of emails. html-to-text hasn't seen a release since March 2023 and appears to be no longer maintained.

This causes downstream projects to be stuck on older transitive dependencies with no path to upgrade.

It might be worth exploring alternatives such as the rehype ecosystem (rehype-parse + hast-util-to-text), which is actively maintained and avoids the stale dependency chain.

[gabrielmfern]

hast-util-to-text hasn't had a release in 2 years as well, though I think it'd be a better ecosystem to be around, and seems to be much, much more minimal, but either way it would be a breaking change to switch since we use expose the options for htmlToText right now