added add-username.txt to contributors folder via branch
added add-username.txt to contributors folder via branch

rkaranam/patchwork,Soumya08pragya/patchwork,Frankyx93/patchwork,diegobust4545/patchwork,elzbeth/patchwork,gtbay707/patchwork,Misatoteen/hello-world,SarahSexton/patchwork,laurenamy/patchwork,colpac64/patchwork,SaraHal/patchwork,apound01/patchwork,carufenon/patchwork,juliozm20/patchwork,cadazab/patchwork,joysjsj/patchwork