Public roadmap improvements

[SpennyNDaJets]

trafficstars

• Automated process
• Where is all the stuff that we've shipped? Should we have anything in there, and maybe consider grouping things we've shipped in the past into quarterly or yearly buckets?
• Maybe unrelated to this PR and more about how we're using the GH project, but I wonder if we should worry about these groups like OTel Support + Integrations and Product Polish. I doubt users care about that stuff as much as they do the individual features like "Rust SDK" or "Mobile Session Replay." I wonder if we should reconsider the groupings or maybe just remove them?
• Do we have a way for user-submitted issues to get into the roadmap? Wondering if we have a good mechanism for capturing user ideas and slotting them into our roadmap.

[linear[bot]]

HIG-5136 Automate the public roadmap