Free Xon - Conversation Improvements 2.5.1

• Fix adding a recipient to a direct message would re-index the conversation twice with XF2.3
• Fix check with XF2.2 for starting a conversation without recipients

• For XF2.2, require re-indexing of conversations & conversation messages!
• Require StandardLib v1.21.0+
• Require Search Improvements v2.16.0+
• XF2.3 support
• php 8.4+ compatibility fixes
• Remove "Allow conversations with no one" option. XF2.3 supports this by default

• Add "silently edit" feature for editing conversation messages, requires the "edit any message" permission

• Fix edited conversation messages lacked the "Last edited:" marker after they had been edited

• Fix mysql-based search support not returning conversation search results when using the conversation search tab