Add some info to Perfomance analyzer docu

https://doc.qt.io/qtcreator/creator-cpu-usage-analyzer.html

I would like to have as a note or just clarification in some sections

To performance analyzer correct work needed:

1. To allow perf events in kernel 
   echo -e "kernel.perf_event_paranoid=-1\nkernel.kptr_restrict=0" | sudo tee /etc/sysctl.d/10-perf.conf
2. need to be installed for Debian(Ubuntu):
   sudo apt-get install linux-tools-$(uname r) linux-cloud-tools$(uname -r)
3.  ./Qt/Tools/QtCreator/libexec/qtcreator/perfparser should be presented
4.  Some info can be found in the application output even if the performance analyzer shows pop-up errors.