feat: add support for breadcrumbs param in front matter for showing/hiding breadcrumbs on specific pages

[ggwicz]

Hi there! Hextra is awesome and I wanted to propose a feature that I've found useful recently: the ability to hide breadcrumbs on specific pages.

This has been especially useful on "index" pages, for example, where even with a custom linkTitle there's just not much value added from the breadcrumb.

I've also included some documentation updates for breadcrumbs in general—and for this hideBreadcrumbs option specifically—as I wasn't finding that information elsewhere.

Example

Before

/docs	/docs/processes/story-points
At my Docs index page (/docs), the title Documentation being repeated twice by the auto-generated breadcrumbs isn't really helpful.	But it is, of course, still helpful once we get into the actual sub-pages, like /docs/processes/story-points in this example:

After

With this new hideBreadcrumbs param, you can have the best of both worlds.

I add it to the front matter of /content/docs/_index.md:

---
hideBreadcrumbs: true
title: Documentation
weight: 10
cascade:
  type: docs
  sidebar:
    open: true
---

And then no longer have it on the /docs page, but all the other breadcrumbs generation continues to work exactly the same.

/docs	/docs/processes/story-points

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[imfing]

Hi @ggwicz, thank you for the PR. I was also thinking about adding this recently.

I wonder if changing the flag name from hideBreadcrumbs to simply:

---
breadcrumbs: true # or false
---

would make more sense, similar to the toc flag.

[ggwicz]

Yeah good call @imfing! Fixed!

[imfing]

Great work, appreciate for adding the doc @ggwicz