Host stuff locally (#194)

This commit includes the following things to host them locally:
* fonts (formerly from Google Fonts)
* fontawesome
* normalize

For a reasoning on why this is good to do, see below.

Everything is now included in Sass code. This means not only we no more
have requests to third-party sites, but also reduced the amount of
requests necessary to access the page by three.

I mainly downloaded all necessary stuff and put it at appropriate
places. I also ran `make release` to regenerate all CSS files.

Sites that helped me doing this:
* https://switching.social/ethical-alternatives-to-google-fonts/
* https://google-webfonts-helper.herokuapp.com/fonts
* https://google-webfonts-helper.herokuapp.com/fonts/lato?subsets=latin-ext,latin
* https://google-webfonts-helper.herokuapp.com/fonts/merriweather?subsets=vietnamese,cyrillic-ext,latin-ext,latin,cyrillic
* https://google-webfonts-helper.herokuapp.com/fonts/source-code-pro?subsets=latin-ext,latin
* https://fontawesome.com/how-to-use/on-the-web/using-with/sass
* https://github.com/JohnAlbin/normalize-scss

---------------

Currently, this theme opens many connections to third-party sites.

I hope I don't have to explain all too much why not exposing all visitors to Google etc. is a good thing, but I'll do list some advantages:

* Pretty strong CSP: `content-security-policy: default-src https://nico.dorfbrunnen.eu:443`
* Increased autonomy of webpage; if Google or other CDNs goes down, website still looks good
* When building locally without Internet, everything works fine
* Google is all about surveillance capitalism, they want to collect as much data about people as possible
* With this change, we stop helping them on all websites using this theme
* Google (and the other sites might too) is censored in quite some countries; in all of them, this theme would look not as beautiful as it could

Regarding licensing issues:

> first I need to understand if there is any license problem if we distribute these fonts with the theme.

Sure! Here's what I've found out:

According to [the CSS file we pull from Google](https://fonts.googleapis.com/css?family=Lato:400,700%7CMerriweather:300,700%7CSource+Code+Pro:400,700) we're using three fonts: [Lato](https://fonts.google.com/specimen/Lato), [Merriweather](https://fonts.google.com/specimen/Merriweather) and [Source Code Pro](https://fonts.google.com/specimen/Source+Code+Pro). On the bottom right of those pages it says for all fonts that they are licensed under the [Open Font License ](http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=OFL_web). In its preamble, it says:
> The OFL allows the licensed fonts to be used, studied, modified and redistributed freely as long as they are not sold by themselves. The fonts, including any derivative works, can be bundled, embedded, redistributed and/or sold with any software provided that any reserved names are not used by derivative works.

So I think we're good to go and can include those fonts with the theme.