chore(docs): update roadmap

[krancour]

A bit of roadmap cleanup:

• Present what's behind us in the past tense
• Defer things not accomplished in v0.3.0 to v0.4.0
• Clarify where we currently are on the roadmap
• Minor formatting improvements

[netlify]

✅ Deploy Preview for docs-kargo-akuity-io ready!

Name	Link
🔨 Latest commit	f6fabb2
🔍 Latest deploy log	https://app.netlify.com/sites/docs-kargo-akuity-io/deploys/6585e34af580f40008238d68
😎 Deploy Preview	https://deploy-preview-1325.kargo.akuity.io
📱 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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (13ae37d) 45.84% compared to head (f6fabb2) 45.84%.

Additional details and impacted files

@@             Coverage Diff              @@
##           release-0.3    #1325   +/-   ##
============================================
  Coverage        45.84%   45.84%           
============================================
  Files              135      135           
  Lines            11560    11560           
============================================
  Hits              5300     5300           
  Misses            6069     6069           
  Partials           191      191           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.