style: make header fixed

[IgnaceMaes]

Builds on top of #185

Makes the header sticky, so all navigation is accessible when scrolling.

[netlify]

✅ Deploy Preview for guidemaker-ember-template ready!

Name	Link
🔨 Latest commit	cb4e05f
🔍 Latest deploy log	https://app.netlify.com/sites/guidemaker-ember-template/deploys/65d70cf208f4b0000895f9b7
😎 Deploy Preview	https://deploy-preview-187--guidemaker-ember-template.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[mansona]

So I love the other 2 sticky PRs but I actually don't think we want this 🤔 we can discuss it at one of our meetings if you like?

[IgnaceMaes]

Mostly based this on other docs websites which mostly all have a sticky header. I do see the benefit of always having the search field available without having to scroll to the top.

I think the other stickyness updates work fine without this. I agree it is odd that we would make the header sticky here while it isn't on other pages using the same component.

Let's pick it up in a sync, or just leave it out for the time being.