updated README.md of the GP Guiding feature
updated README.md of the GP Guiding feature

simonct/phd2,OpenPHDGuiding/phd2,OpenPHDGuiding/phd2,simonct/phd2,OpenPHDGuiding/phd2,simonct/phd2,simonct/phd2,OpenPHDGuiding/phd2,simonct/phd2,simonct/phd2,OpenPHDGuiding/phd2,OpenPHDGuiding/phd2