I'd like there to be a plugin system for sqlite-utils, similar to the datasette/llm plugins. I'd like to make plugins that would do things like:

• Register SQLite extensions for more SQL functions + virtual tables
• Register new subcommands
• Different input file formats for sqlite-utils memory
• Different output file formats (in addition to --csv --tsv --nl etc.

A few real-world use-cases of plugins I'd like to see in sqlite-utils:

• Register many of my sqlite extensions in sqlite-utils (sqlite-http, sqlite-lines, sqlite-regex, etc.)
• New subcommands to work with sqlite-vss vector tables
• Input/ouput Parquet/Avro/Arrow IPC files with sqlite-arrow