Disallow self assignment of properties (no-self-assign)

[feross]

The no-self-assign rule is already enabled, however in ESLint 5 the default options object for the rule has changed from { props: false } to { props: true }.

I like this change, so let's keep it, assuming breakage isn't too high.

https://eslint.org/docs/rules/no-self-assign

[feross]

This rule was actually enabled in a prior upgrade of ESLint. I set the option explicitly nonetheless.