Provide EditorConfig information

Summary:
.editorconfig is a standard some editors recognize for basic styling
options like ident style.

We provide the Nasqueron defaults, with JSON and YAML at 2 spaces instead of 4,
to adhere with the current style of the repository.

Test Plan: Tested in Atom

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1123