updating the help page

[HenrikeW]

Related issue(s) and PR(s)

This PR closes #469

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other

List of changes made

• the overview screenshot was updated
• the descriptive text was updated
• a section about known limitations was added
• the html was made more semantic / unnecessary divs were removed

Screenshot of the fix

Testing

• Read the new help page and make sure it's understandable and matches the current state of the service

Further comments

Definition of Done checklist

• I have made an effort making the commit history understandable
• I have performed a self-review of my own code and commented any hard-to-understand areas
• Tests and lint/format validations are passing
• My changes generate no new warnings

[KattisLej]

Starting review

[KattisLej]

The pictures that need update are in place and the explanation texts are well formulated. I think it looks very good.

[jonandernovella]

I need to zoom in a lot to comfortably read the help page. I think it would be good to zoom in a bit more when making the screenshot.