We are implicitly following parts of the Google C++ style guide, but as we are taking some departures from it (e.g., exceptions, user-defined literals, etc.), we should do one of the following:

• publish a complete style guide on what features we will or won't use, OR
• publish a style guide that's a diff based on the Google C++ style guide

At the very least, we should clarify that we're using only what's available in C++11 and Abseil. Other questions might be around what can be brought in from other third-party libraries, e.g., Boost, which the Google C++ style guide also has a section on.

Without such clarification, it's unclear what contributors can use for development and what they can't (or at least, shouldn't).