Add hooks for adding and modifying tools

[tomepajk]

I was thinking about starting to set up filters to enable other plugins to modify / add tools.

How does the wpcli_ai_ as a prefix sound?

Suggestions for hook places:

• https://github.com/swissspidy/ai-command/blob/8e3982b877b42fcc63ac2ee98df962aaf93a32ab/ai-command.php#L40
• https://github.com/swissspidy/ai-command/blob/8e3982b877b42fcc63ac2ee98df962aaf93a32ab/src/Tools/MapRESTtoMCP.php#L106