[issue31715] Add mimetype for extension .mjs

[Myles Borins]

Myles Borins <mylesborins at google.com> added the comment:

Also wanted to point out some prior art of a mimetype (json) being backported to all active runtimes

https://bugs.python.org/issue30824#msg297527

----------

_______________________________________
Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue31715>
_______________________________________