Add `no-useless-string-literal`

[Yosuke Ota]

Description

no-useless-string-literal rule reports the string alternatives of a single character.
They can be placed outside \q{...}.

/* ✗ BAD */
var foo = /[\q{a}]/v // => /[a]/v
var foo = /[\q{a|bc}]/v // => /[a\q{bc}]/v

/* ✓ GOOD */
var foo = /[\q{ab|}]/v