Add API feature to get lines of code per programming language

Release notes

Added ability to retrieve lines of code per language for each repository in the API.

Problem to solve

Organizations often want to perform analytics on their code. Understanding how many lines of code exist across all code bases in each language is a useful metric to understand what languages are most commonly used.

Proposal

Add a new API endpoint or expand an existing API endpoint to include lines of code for each programming language.

The existing UI showing percentage of languages used is not sufficient: we need to know the number of lines of code per language.