[BIP Proposal] Add BIP-0093 (Codex32) as application to BIP-0085

In a recent exchange on the Bitcoin Development Mailing List, a proposal was discussed to integrate BIP-0093 (codex32) as an application within BIP-0085. The discussion highlighted two main points of improvement that could enhance clarity for those looking to implement the specification. Firstly, there's a suggestion to include explicit pseudocode for the DRNG to 5-bit extraction process. This addition would likely aid in minimizing variations in implementation by providing a clear, standardized method for this particular process. Secondly, there appears to be some ambiguity around the rule stating "threshold == 0 implies n == 1". While currently noted in the documentation, the recommendation is to elevate this statement to a normative requirement. Doing so would clarify its importance and ensure that implementers treat this rule with the appropriate level of significance. These adjustments are aimed at streamlining the integration process and facilitating a more uniform adoption of BIP-0093 within the broader framework of BIP-0085.