Allow other characters than `,` as separators while importing a CSV

[Avinash Sajjanshetty]

You can create a new db from CSV:

turso db create --from-csv test12_sanitized.csv --csv-table-name some_table

but this assumes, as a separator character. Add an optional flag --csv-separator which takes the separator character like:

turso db create --from-csv test12_sanitized.csv --csv-table-name some_table --csv-separator ";"

reported here: https://discord.com/channels/933071162680958986/1215308443217563668/1215308443217563668