Plug-in parameter groups

[t0m]

https://github.com/WeAreROLI/JUCE/commit/b26495491b3ca03d193157c9f8ef52036d70e5a7

auto param = apvts.createParameter (...);
addParameterGroup (std::make_unique<AudioProcessorParameterGroup> ("gid", "GROUP A", " | ", std::move (param)));