Move [ERR] [ERROR] and similar to separate OpenType feature outside of calt

[svipas]

When writing code in some cases it renders incorrectly, because ligatures like [ERR], [ERROR] are in calt. My suggestion is to move it to separate OpenType feature for e.g. ss15.

const [err] = someFn()

[fabrizioschiavi]

This makes sense. Thanks @svipas !