feat: Docset archiving

[gavinelder]

The PR introduces the concept of doc-set archiving using Netlify immutable URLS inspriation

Note for reviewers

This PR is based on work to fix theming in side of #788 as such it contains multiple commits please refer to

0ac0935

To see the relevant changes.

Outstanding Questions.

1. Is the main docs URL actually immutable I am not 100% certain of that however if it's not we should be able to use redirects by using the previous doc-set build with the Enteprise docs URL for example.

[[redirects]]
  from = "https://docs.seqera.io/platform-enterprise/23.3/*"
  to = "https://68a533878b0a6b000842d7ab--seqera-docs.netlify.app/platform-enterprise/23.3/:splat"
  status = 200

2. What do we do when we want to redesign the docs site ?

As we're no longer rebuilding this content do we want to accept that if you look at a very old version the site will be different.

3. How many versions do we want to archive ?

from @llewellyn-sl

It does, though we may want to only mark n-3 and earlier as archived, as our support SLA is n-2

4. Do we want to show the "archived" name in the doc-sets.

If we are content with the way of doing redirects etc we could potentially not show archived or have another item such as - deprecated or locked.

[netlify]

✅ Deploy Preview for seqera-docs ready!

Name	Link
🔨 Latest commit	df99191
🔍 Latest deploy log	https://app.netlify.com/projects/seqera-docs/deploys/68a58a051afaa400087e6946
😎 Deploy Preview	https://deploy-preview-790--seqera-docs.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 project configuration.