Add IDs to all section headings in the website

[waldyrious]

So they can be easily linked to. Even better if hovering the headings reveals a ¶, §, 🔗 or some other symbol that indicates the section is linkable (as is the case e.g. in GitHub READMEs).

[arun-is]

Let me quickly add ids to the items. I'll ponder how to design the hover to show link icon functionality

[waldyrious]

Thanks for addressing this in #67! To clarify, I was thinking about having links in section headings of the main page, e.g. "We think spatially" and "What makes an infinite canvas?" (I wanted to link the latter in #53, for example). Could those IDs be added as well?

Same for the sections in the History page. :)