Add pp 13.6 cfg with tuned diffractive events

Author: njacazio

MC/config/ALICE3/ini/pythia8_pp_136tev_inel_difftuned.ini

@@ -0,0 +1,9 @@
+[Diamond]
+width[2]=6.0
+
+[GeneratorExternal]
+fileName=${O2DPG_MC_CONFIG_ROOT}/MC/config/ALICE3/pythia8/generator_pythia8_ALICE3.C
+funcName=generator_pythia8_ALICE3()
+
+[GeneratorPythia8]
+config=${O2DPG_MC_CONFIG_ROOT}/MC/config/common/pythia8/generator/pythia8_inel_difftuned.cfg