Add: Announcement post for 15.0

[2TallTyler]

Comments and suggestions welcome on the shortlist of new features. I did not intentionally place my features first; it just made sense to me to cover map generation first.

I have been talking with Master Hellish about this video of the new features, and got permission to include the link here. I think it's a good addition to our usual text-heavy changelog, especially with the size of this release!

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Long news:

New Year, New You, New OpenTTD!

OpenTTD 15 is now out and ready for you to play!

New features include:
* Companies in multiplayer no longer have passwords, invite specific players using buttons in the Online Players list instead
* Island maps can be surrounded by infinite water instead of void
* Rivers can end in wetlands if unable to reach sea
* Bridges can be placed over stations and road stops
* Roads can now have waypoints
* Houses can be placed manually
* Industries and towns have graphs of their cargo history
* Improvements to menus, including a new main menu and a combined game options and settings window
* Many more features, changes, and fixes

For a full breakdown of new features, check out [this video by Master Hellish](https://www.youtube.com/watch?v=Q3iDSxrqAPE).

Full news: https://www.openttd.org/news/2026/01/01/openttd-15-0

Short news:

New Year, New You, New OpenTTD! Now available on Steam / our website.
https://www.openttd.org/news/2026/01/01/openttd-15-0

Image:

News-15.0.zip