Language Enhancement Proposals reference manual

Our languages’ concepts and changes each are set in stone in a Language Enhancement Proposal (LEP), inspired by the [PEP system for Python](https://www.python.org/dev/peps/). They describe the reasoning and functionality and form a reference for all the language’s implementations.

LEPs serve as the basis for our languages and therefore require technical specifications. LEPs are proposed and managed within a versioned repository, which also serves as the way of tracking their revision history. Each contains an abstract, rationale, technical functionality and concise examples section.