New: Add space-unary-ops rules (#1346)

This rule will require or disallow space before or after unary operators (words and non-words). This rule references [issue#1346](https://github.com/eslint/eslint/issues/1346)
This paragraph should be under "Rule Details". The first section is just an introduction to the concept that the rule addresses, not about the rule itself. You could also add a few examples in this section to show the difference.