[Feat] docs: Add mkdocs tag to tool headers

[cwhite911]

Currently we are setting keywords in each tools md header, however we can take advantage of material for mkdocs' built in tags plugin for page categorization.

# mkdocs.yml
plugins:
  - tags

Current header of r.profile

---
name: d.profile
description: Plots profile of a transect.
keywords: display, profile, raster, plot
---

Header with tags support:

---
name: d.profile
description: Plots profile of a transect.
tags: display, profile, raster, plot
---

[petrasovaa]

Could you explain what is the advantage specifically? I couldn't quite understand what the plugin does.

[cwhite911]

It's the material mkdocs way of doing what we are doing with keywords. Some advantages are nice icon integration and an automated tags index. We don't need to do this right away, but I think it looks nice.

[wenzeslaus]

I like the plugin and we already have rich keywords. I would knock down other things first though since we have system for keywords already in place and it has its own sophistication. It will be nice to drop that custom code at some point though.