refactor(monorepo): editor-core-types

[bryphe]

With #2312 and #2313 - moving in reason-tree-sitter and editor-input - we can now move editor-core-types into Onivim proper.

The reason behind this is to update some of the common types - like Index.t and Range.t - they are not quite setup in a way where we can fully benefit from the type-system. In particular, we don't have typing around byte position vs UTF-8 character position vs screen column - they are just all ints or Index.ts. We should be able to leverage the type-system for this, and have auxiliary types, like ByteRange.t, so that we can be explicit in our APIs to document whether a function expects a byte index, character index, etc, and have it enforced by the compiler.