Update whitenoise to 5.3.0

[pyup-bot]

This PR updates whitenoise from 5.0.1 to 5.3.0.

Changelog

5.3.0

------
* Gracefully handle unparsable If-Modified-Since headers (thanks
`danielegozzi <https://github.com/danielegozzi>`_).
* Test against Django 3.2 (thanks `jhnbkr <https://github.com/jhnbkr>`_).
* Add mimetype for Markdown (``.md``) files (thanks `bz2
<https://github.com/bz2>`_).
* Various documentation improvements (thanks `PeterJCLaw
<https://github.com/PeterJCLaw>`_ and `AliRn76
<https://github.com/AliRn76>`_).

5.2.0

------

* Add support for `relative STATIC_URLs <https://docs.djangoproject.com/en/3.1/ref/settings/#std:setting-STATIC_URL>`_
in settings, as allowed in Django 3.1.
* Add mimetype for ``.mjs`` (JavaScript module) files and use recommended
``text/javascript`` mimetype for ``.js`` files (thanks `hanswilw <https://github.com/hanswilw>`_).
* Various documentation improvements (thanks `lukeburden <https://github.com/lukeburden>`_).

5.1.0

------

* Add a :any:`manifest_strict <WHITENOISE_MANIFEST_STRICT>` setting to prevent
Django throwing errors when missing files are referenced (thanks
`MegacoderKim <https://github.com/MegacoderKim>`_).

Links

• PyPI: https://pypi.org/project/whitenoise
• Changelog: https://pyup.io/changelogs/whitenoise/
• Homepage: https://whitenoise.evans.io