[nested] Nested selectors are not calculated properly with `$` in it

Expected behavior: Nested selectors should include escaped $ in its parent's selector

Describe the bug: selectors that are nested drop the $ and keep the escape backslash, while their parent selector includes \$.

1. Open up https://cssinjs.org/repl
2. On line 23, change the selector to '$Button' or '\$Button'
3. Observe the nested selectors generated

The issue happened in my react app where components are mangled by webpack, and some of them starts with $ (like $z). In that situation, the nested selectors do not work.

Codesandbox link: Just use the https://cssinjs.org/repl

Versions (please complete the following information):

• jss: 10.0.0
• Browser [e.g. chrome, safari]: chrome
• OS [e.g. Windows, macOS]: windows Feel free to add any additional versions which you may think are relevant to the bug.