Replace Room.findPath opts.heuristicWeight explanation with version from PathFinder opts to resolve markdown italics mistake

[sparr]

Currently Room.findPath opts.heuristicWeight has some unescaped asterisks that produce italic text instead of being readable.

Corrected version copied from

docs/api/source/PathFinder.md

Line 125 in f96f462

<div class="api-arg-desc">Weight to apply to the heuristic in the A\* formula <code>F = G + weight \* H</code>. Use this option only if you understand the underlying A\* algorithm mechanics! The default value is 1.2.</div>

I also searched for any other instances of this and didn't find any; all the other un-escaped asterisks are in contexts that don't require escaping (e.g. code blocks).