Internationalization

[arianvp]

Once #2 is solved, this is a matter of someone translating the markdown files I think...

[arianvp]

Update: Internatiionalization support is in place. just need to translate everything :)

We have to add a language switcher. Template can be found here: https://nl-design-system.gitlab.io/nl-design-system/componenten/footer/index.html

[bwbroersma]

Now I see I should have chosen the key payoff instead of tagline in the translation and footer file :slightly_smiling_face:.

I think we should include both a header and footer language switcher, like on the RIVM website.

Header:

Footer:

[EdoPlantinga]

Recently did a major content revision. Open to an EN language translation.