Fix issues in https://web.dev/measure

[Lvl4Sword]

According to https://lighthouse-dot-webdotdevsite.appspot.com//lh/html?url=https%3A%2F%2Fpythondiscord.com ( through https://web.dev/measure ), the Python Discord site currently scores 74/100 in Performance, 86/100 in Accessibility, 100/100 in Best Practices, and 91/100 in SEO.
These seem like some relatively easy things to implement for the speed ( and other ) bonuses they offer.

[lemonsaurus]

Here are actual actionable points:

Don't load unused Bulma Extensions

Currently, we're not defining the extensions key in our BULMA_SETTINGS config dict. This means that all Bulma extensions are being loaded, which is stupid because we're not using any of them afaik.

To solve this, just add extensions=[] to BULMA_SETTINGS.

Off-site asset loading has bad caching policies

We're loading a few assets from off-site - the Django logo from djangoproject.com, and some code jam banner from the githubusercontent CDN. These both have bad caching policies as a result. Fetch these images, add them to the site, and update the references to the local ones instead.

Resource-blocking assets

We don't preload CSS, and we don't defer loading of JS. This should be fixed.

This fix mostly needs to happen in django-simple-bulma, so see lemonsaurus/django-simple-bulma#45 - but we may be importing other stuff (local css, maybe fontawesome?) that could use this treatment as well.

Minification of JS and CSS

We don't minify JS and CSS.

Same story here - this mostly should be addressed in django-simple-bulma (lemonsaurus/django-simple-bulma#44) but may need to be addressed for a few local files as well.

Images should be the right size

There's probably some images resized by width and height parameters or css - this is wasteful compared to just serving them at the right size. So, just resize those assets and remove the resizing.

[MarkKoz]

@Lvl4Sword Are you still working on this?