Use the correct type for layer properties

[InnocentusLime]

Synopsis

The Layer struct used a HashMap to encode the properties instead of Vec<Property>. Which made macroquad_tiled crash when it tries to parse a map where there is a layer that has custom properties. This is because they are stored the same way as everywhere else.

What is done

• Simply replace the type with Vec<Property>
• Also added a link to the tiled docs for the Layer struct