Code Style Guide

Now, I'm using default firebase functions code style for linting (with eslint), but I'm pretty open to anything we feel confortable with. Discussion open ^^

My 50 cents: I preffer indent using tabs instead of spaces :rofl:

Review the repository's Firebase Functions linting setup and the current ESLint conventions before proposing any change. The issue needs an agreed style decision first; done would mean the chosen conventions are clearly documented and consistently represented in the project configuration.

Written by the indexing model from the issue text.