Roadmap kanban board requires horizontal scrolling on mobile

On mobile, the public roadmap page (/roadmap) shows the Planned / Progress / Completed columns as a fixed-width horizontal row, so you have to scroll sideways to see all columns. The columns should stack one after another vertically on small screens so the whole board is readable with normal vertical scrolling.

Fix PR: https://github.com/mcnaveen/feedbackjar-monorepo/pull/27