**Is your feature request related to a problem? Please describe.**
After webContents.insertCSS() I cant find a way to remove injected stylesheet.

**Describe the solution you'd like**
insert: webContents.insertCSS('style-id', 'body { ... }') or .inserCSS('body { ... })'
remove: webContents.removeCSS('style-id') or .removeCSS() to remove all injected stylesheets


atom/renderer/api/atom_api_web_frame.cc
int world_id) final {
    
    
    UnsetAndDestroy();
  }
 private:
  static std::set<SpellCheckerHolder*> instances_;
  std::unique_ptr<SpellCheckClient> spell_check_client_;
};
}  
std::set<SpellCheckerHolder*> SpellCheckerHolder::instances_;
void SetName(v8::Local<v8::Value> window, const std::string& name) {
  GetRenderFrame(window)->GetWebFrame()->SetName(
      blink::WebString::FromUTF8(name));
}
void SetZoomLevel(v8::Local<v8::Value> window, double level) {
  content::RenderFrame* render_frame = GetRenderFrame(window);
  mojom::ElectronBrowserPtr browser_ptr;
  render_frame->GetRemoteInterfaces()->GetInterface(
      mojo::MakeRequest(&browser_ptr));
  browser_ptr->SetTemporaryZoomLevel(level);
}
double GetZoomLevel(v8::Local<v8::Value> window) {