Add a simple language overview

[wilzbach]

Reboot of #119 (with working links this time)

[wilzbach]

Please use internal link format here and not the external. It's an internal link after all and this will force a change of the domain when you're on tour.dlang.io and force a change to HTTPs if you're on HTTP. Additionnaly this prevents local testing after all...

• This was/is blocked by Fix markdown link parser core#472, because at the moment the link checking is broken.
• AFAIK we want to force SSL anyways
• Links are also checked directly if only one repository is enabled (e.g. with --lang-dir), which would lead to an error (with the Fix markdown link parser core#472 absolute links shouldn't be checked anymore during development)

[JackStouffer]

Can we use the HTTP header Accept-Language to redirect people automatically?

[wilzbach]

Can we use the HTTP header Accept-Language to redirect people automatically?

Of course, but most translations aren't finished yet.
I opened an issue at the base repo: dlang-tour/core#496
(this repo just contains content)

I will merge this now as the previous PR has been approved and this is hasn't received any activity for more than a month.

[PetarKirov]

I will merge this now as the previous PR has been approved and this is hasn't received any activity for more than a month.

Sure, glad to see this finally in!