Add example for profiler.enable with xdebug profiling enabled

[glensc]

This adds an example to Detect XDebug triggers and skip profiling:

• Detect XDebug triggers and skip profiling xhgui#104

See perftools/xhgui#104 (comment)

[glensc]

This needs to be validated first as xdebug_is_enabled() description in phpstorm stubs says "Return whether stack traces would be shown in case of an error or not"

• https://github.com/JetBrains/phpstorm-stubs/blob/v2020.2/xdebug/xdebug.php#L129-L133

[glensc]

Perhaps xdebug_info gives he accurate info:

➔ php -r "xdebug_info();"|grep -i xdebug.mode
xdebug.mode => develop => develop

which is just in value:

$ php -r 'var_dump(ini_get("xdebug.remote_autostart"));'
string(1) "0"