Add example of using yarn test with arguments (#1383)
Add example of using yarn test with arguments (#1383)

Not sure if the copy is great, but since this is mostly for n00bs, better to err on side of more information.
rattrayalex/prettier,arijs/prettier-with-tabs,azz/prettier,despairblue/prettier,Skywalker13/prettier-space-parenthesis,azz/prettier,yamafaktory/prettier,arijs/prettier-miscellaneous,arijs/prettier-miscellaneous,despairblue/prettier,existentialism/prettier,existentialism/prettier,arijs/prettier-miscellaneous,Skywalker13/prettier-space-parenthesis,Skywalker13/prettier-space-parenthesis,arijs/prettier-with-tabs,arijs/prettier-miscellaneous,lydell/prettier,rattrayalex/prettier,azz/prettier,jlongster/prettier,prettier/prettier,Skywalker13/prettier-space-parenthesis,prettier/prettier,azz/prettier,prettier/prettier,lydell/prettier,existentialism/prettier,lydell/prettier,yamafaktory/prettier,rattrayalex/prettier,lydell/prettier,existentialism/prettier,prettier/prettier