Add setup guide structure and preview workflow

[benhg]

Adds the setup guide structure for event and equipment guides.

Included guide pages:

• Pacificon setup guide
• Field Day setup guide
• KLM KT36 equipment setup guide

Also adds the preview Pages workflow that was present in the working tree for this branch.

Newsletter automation has been removed from this PR.

[kn6yuh]

I suggest you add the TOC in each of the pages, as it makes it much easier to navigate and see what's on a page.

---
**Table of Contents**
* Table of Contents
{:toc}
---

Check any other page for examples of where it's placed.

I'm not going to block you on merging this, so you can add the TOC at a later PR if you prefer.

Where will this be linked in the main website? We could add a separate navigation section, or add it to the events template. Ideas?

[kn6yuh]

I thought this was ready for review :) Moved it back to draft.