[DOC] Roadmap updates

[peytondmurray]

Description

This pull request updates the roadmap:

• Explicitly adds an item for making a plugin system for locking, solving, and package management
• Adds links to issues for a number of items that were missing them

Pull request checklist

• [x] Did you test this change locally?
• [x] Did you update the documentation (if required)?
• [x] Did you add/update relevant tests for this change (if required)?

[netlify[bot]]

✅ Deploy Preview for conda-store ready!

Name	Link
🔨 Latest commit	d9b2e5fbec51539e99b053d51f987ef4ead13cc7
🔍 Latest deploy log	https://app.netlify.com/sites/conda-store/deploys/67294cd317e19c00080c4698
😎 Deploy Preview	https://deploy-preview-958--conda-store.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.