Updated BIP for OP_CAT

In a recent update to the Bitcoin Improvement Proposal (BIP), a significant modification was made to specify the theoretical maximum of public keys. This adjustment can be viewed in detail through the commit available at GitHub. The conversation also touches upon the potential for innovation in the realm of tree signatures within the BIP framework, suggesting an interest in seeing proposals in this area developed and submitted for consideration. This indicates a willingness to explore and possibly incorporate more complex signature schemes into the Bitcoin protocol, potentially offering enhanced security or efficiency benefits.