0.21.4

This is a small but an important update.
It is important because it adds proper decoding of placeholder passes; any HT compliant decoder should support them.
It also fixes a bug in avx512 encoder, as detailed in #188.

What's Changed

• This should fix the problem for the time being #188. by @aous72 in #190
• Placeholder passes by @aous72 in #191

Full Changelog: 0.21.3...0.21.4