Mountain lines idea

Since this is like a world/country map, why not also have mountain lines added?
By that I mean the lines you can see on maps indicating a change of elevation.

Star count could be used to determine the "height".
One other way could be making a heatmap.

No files, tests, or entry points are named. Start by reviewing how the country map is rendered and how star counts are represented, then define whether elevation should use contour lines, a heatmap, or another visualization before implementation.

Written by the indexing model from the issue text.