RFC: Absolute Require Syntax

[bradsharp]

This RFC proposes additional syntax for require by string that allows modules to be resolved relative to the root of a project or library. It is based on #78 which proposed the same changes but also removed relative paths.

Rendered.

[vegorov-rbx]

This really sounds how we wanted to have libraries to work initially.
We explored both having an alias path '@' to point to the root of the library as well as just having library root '.' in paths inside luaurc to resolve non-relative requires from module root. That was before we removed absolute requires.
This really sounds like the later, but codified implicitly without a need to place '.' in each library luaurc file.
Sounds good and I don't think it even interacts with relative requires, so any problems with that can still be fixed separately if desired.