Add possibility to use the CLI programmatically

[NicolasBonduel]

This pull request adds the possibility to use the CLI programmatically. This is useful for using LogRocket as part of a webpack flow for example.

Here is an associated repository for a webpack plugin using my fork: https://github.com/NicolasBonduel/webpack-logrocket-plugin

This change was inspired by this Sentry plugin: https://github.com/getsentry/sentry-webpack-plugin