[site] Documentation doesn't have anchor links to headers, anchor scrolls too low

[paskal]

1. I've tried to find an anchor like https://remark42.com/docs/configuration/email/#admin-notifications on the page itself and didn't find it, would be nice to have a link to it next to the header.
2. After going by the anchor, the header itself is covered by the navigation of the site which is unexpected, I would expect the header I'm linking to be completely visible. Here is the state right now after opening https://remark42.com/docs/configuration/email/#admin-notifications in Safari: What I expect to see after going by the link:

[vanyauhalin]

Hi, I have added implementation of anchor links in this pr. This solved the first point, but not the second.

[Jaskon]

This pr tries to solve the second point

[paskal]

I'm okay with the lack of mentions of the anchor links. At least they work properly now, thanks to @Jaskon. Resolving this issue.