Lexicographical sorting of object keys

[LinusU]

A bit similar to #561, but this is for every object literal.

There is an ESLint rule for this:
https://eslint.org/docs/latest/rules/sort-keys

Since ESLint are removing formatting rules, they have not accepted pull requests to implement auto-fixing of that rule, it instead lives in a separate repo:
https://github.com/leo-buneev/eslint-plugin-sort-keys-fix

This is very useful in larger codebases where multiple people commit to, in order to reduce merge conflicts if everyone is always appending new keys to the end of objects.

Example:

- let obj1 = {a: 1, c: 3, b: 2}
+ let obj1 = {a: 1, b: 2, c: 3}