Add cli check for common src directory

[daveycodez]

https://github.com/aspen-cloud/triplit/blob/7acfdf9b8012d947060d899f94cdf7aa069cab67/packages/cli/src/filesystem.ts#L14

const BASE_PATH = fs.existsSync(path.join(CWD, 'src')) ? 'src/' : ''
export const TRIPLIT_DIR = path.join(CWD, `${BASE_PATH}triplit`);

[ahrorbeksoft]

so, are we having it or not?