Change the sun shelter image make it clearer it's for shade only

[andrewharvey]

The current sun shelter image is this

https://github.com/Helium314/SCEE/blob/42cf10eda9eb4bd5fc4023b786845b1a940ccf15/app/src/androidMain/res/drawable-hdpi/shelter_type_sun_shelter.jpg

I find that this is too similar to the other shelter type photos. What sets sun_shelter apart is that it it's primarily designed to provide shade from the sun, and provides little to none protection from the rain.

I think using a a photo of a shade sail would work better, any of the photos from
https://wiki.openstreetmap.org/wiki/Tag:shelter_type%3Dsun_shelter#Examples except the last one would work.

[mnalis]

I like this one: https://wiki.openstreetmap.org/wiki/File:Strathmerton_Brian_Pinnuck_Memorial_Park_Playground.JPG (if it still looks good when small / cropped)