Sidebar Icons

[Grabsky]

I don't think this needs much explanation. Icons can make sidebar much more readable. Nearly every static site generator I was using for docs, had first-party support sidebar icons.

Configurable in hugo.yaml for static sidebar entries, and per-document / directory via top-level property.

---
title: "Getting Started"
type: docs
icon: icon-name
---

Ideally, should support Heroicons as well as data/icons.yaml.

Considered Alternatives

I did consider using emojis instead but it isn't viable for number of reasons.

• Emojis can look different on each platform / device, and can be too detailed for small font sizes.
• Emojis are inconsistent and not rendered in monochrome, which can actually lead to more sidebar clutter.
• Emojis simply lack a lot of symbols.

[imfing]

I created a feature request issue from this #961

I think the icon support implementation is trivial, will add it along with the sidebar revamp for the next version hopefully