Reports hashes with strings as keys. It is preferable to use symbols instead of strings as hash keys.

Example:

# Bad practice
{ 'foo' => 1, 'bar' => 2 }

A quick-fix is available to convert all string keys to symbols. After the quick-fix is applied, the result looks like this:

# Good practice
{ foo: 1, bar: 2 }

Inspired by 'RuboCop'