Feature Request: support --verbose=<level>

[jshort]

I was debugging an app that uses cxxopts and easyloggingpp and realized that the easy logging setup was not respecting --verbose=9 but it does work with -v 9 or --verbose 9. Is there a reason standard long option format with an equals sign does not work?

The documentation says --v=9 should work but cxxopts throws an exception on this anyway but it seems to be an atypical option style (half short option half long option with equals arg).