Improve docs as landingpages

[norgeindian]

According to Google Search Console, our docs pages are pretty well ranked.
In my eyes we should try to do the following to use that:

1. Improve the design so that it looks a bit more like our homepage
2. Include more links to our homepage so that visitors are more likely to visit the page as well
3. Improve pages regarding SEO

@sprankhub , what is your opinion regarding that?

[sprankhub]

We discussed that we should integrate the docs into our website. On https://www.customgento.com/extensions/, we will have another button to the respective Docs page, which is another page on our website.

[norgeindian]

Will be handled in https://github.com/customgento/website/issues/318