Document SQLite idempotent script limitations

[bricelam]

Fixes #2636

[bricelam]

I thought about mentioning ways to generate an elaborate bash script with individual migration scripts, but then I figured, "Meh, it's just SQLite." (and bundles will be better anyway)

if [[ $(sqlite3 my.db "SELECT COUNT(*) FROM __EFMigrationsHistory WHERE MigrationId = '00000000000000_InitialCreate'") != 0 ]]; then
    sqlite3 my.db ".read 00000000000000_InitialCreate.sql"
fi

[smitpatel]

Note to shay, github action build check is not running when a PR from fork comes.