add docs about credit
add docs about credit

parasgithub/PrairieLearn,rbessick5/PrairieLearn,parasgithub/PrairieLearn,PrairieLearn/PrairieLearnHack,PrairieLearn/PrairieLearnHack,PrairieLearn/PrairieLearnHack,rbessick5/PrairieLearn,parasgithub/PrairieLearn,jakebailey/PrairieLearn,kevinwang/PrairieLearn,mwest1066/PrairieLearn,parasgithub/PrairieLearn,PrairieLearn/PrairieLearnHack,tbretl/PrairieLearn,mwest1066/PrairieLearn,tbretl/PrairieLearn,jakebailey/PrairieLearn,tbretl/PrairieLearn,kevinwang/PrairieLearn,tbretl/PrairieLearn,mwest1066/PrairieLearn,PrairieLearn/PrairieLearnHack,kevinwang/PrairieLearn,PrairieLearn/PrairieLearnHack,rbessick5/PrairieLearn,mwest1066/PrairieLearn,jakebailey/PrairieLearn,jakebailey/PrairieLearn,rbessick5/PrairieLearn,parasgithub/PrairieLearn,rbessick5/PrairieLearn,tbretl/PrairieLearn,kevinwang/PrairieLearn,kevinwang/PrairieLearn,PrairieLearn/PrairieLearnHack,kevinwang/PrairieLearn,PrairieLearn/PrairieLearnHack,mwest1066/PrairieLearn,kevinwang/PrairieLearn