Update QuickJS to 2020-09-06 release

[littledivy]

Update quickjs to 2020-09-06 release.
bellard/quickjs@7c312df

We're currently using https://github.com/elsaland/quickjs/blob/master/version.h . Marking this as a good first issue.

[sidntrivedi012]

@littledivy I would like to work on it. Just wanted to confirm that we need to update the fork (elsaland/quickjs) and our dependency here , right?

[notfilippo]

Yup! Thanks for taking this issue @sidntrivedi012