Check current output of htmlproofer applied on jekyll build in branch master

There are very few violations detected by htmlproofer in generated HTML regarding the status quo of HIFIS page, which is just the index.html so far. Just to document and keep in mind that these violations might be reported, here is the list:

• image /assets/img/HIFIS_Logo_long_RGB.svg does not have an alt attribute (line 30)
• image /assets/img/Helmholtz_Logo.svg does not have an alt attribute (line 170)
• internally linking to contact.html, which does not exist (line 182)

<a href="contact.html">Contact</a>

• internally linking to imprint.html, which does not exist (line 174)

<a href="imprint.html">Imprint</a>

• internally linking to privacy.html, which does not exist (line 178)

<a href="privacy.html">Privacy</a>

• internally linking to team.html, which does not exist (line 45)

<a href="team.html">Team</a>

Feel free to fix the important parts and close the issue even if some violations remain.