Add check for sqlite3 program [Feature Request]

[kiloforce]

Was running the script, but it wasn't updating the adlist. Starting debugging the logs/script and realized it was calling sqlite3 program, which is not installed on the system. Maybe add a check near the beginning for sqlite3 and error out if it is missing? It's not required to run Pi-hole.

[JavanXD]

Oh, in my installation which is default PiHole on Raspi it was sqlite3, what do you have as dbms?

[kiloforce]

My instance of PiHole is running on Ubuntu 22. I see php-sqlite3 installed, just not the CLI sqlite3 version installed. I installed it so I could use your script.