make site valid in accordance to W3C validator.

[nisarhassan12]

Fixes #868
Addresses the following from gitpod-io/website#842

[nisarhassan12]

Not sure How we can get rid of these errors will look it up later:

Todo

I will inspect later how these can be addressed.

/pricing

I'm done testing most of the pages apart from /docs, individual blog post and Imprint, ToS, Privacy Policy.

[nisarhassan12]

According to W3C we should avoid nesting Links:

But currently, we're doing it on https://www.gitpod.io/blog in the PostPreview Card

Removing the links from the author name would fix this issue. @ChristinFrohne Is this ok to remove the links from the names? Thanks

EDIT

The issue is quite critical that it caused the other errors to be ignored.

[chrifro]

@nisarhassan12 I just noticed that the links to the author's profile are not working anyways. So you can just remove the link completely from the overview page. On each blog post the link to the author's profile needs to be there though.