Support loading of extensions

[Avinash Sajjanshetty]

I want to be able to do something like this:

import os

import libsql_experimental as libsql
import sqlite_vss

print(F"syncing with {os.getenv('LIBSQL_URL')}")
conn = libsql.connect("hello.db", sync_url=os.getenv("LIBSQL_URL"),
                       auth_token=os.getenv("LIBSQL_AUTH_TOKEN"))

conn.sync()
conn.enable_load_extension(True)
sqlite_vss.load(conn)

Depends on tursodatabase/libsql#402