I able to solve the error R10 but idk why maybe i dont have luck one error solve second comes second solves third comes 
so now i am getting this error and for R10 error I forgot to save the changes i made to github thats y i not able to see any changes on the heroku app it would have worked with heroku right as i am using only prismic, express, webpack and all as a techstack.
so the error rn i am trying to resolve is this one:
UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error
originated either by throwing inside of an async function without a catch
block, or by rejecting a promise which was not handled with .catch(). To
terminate the node process on unhandled promise rejection, use the CLI flag `--
unhandled-rejections=strict`
(see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 2)
