add zstd compression support

[cromerc]

Added zstd compression support. To show how useful zstd is I am using it on a map I have that has 141x32 tiles. These are the file sizes of that one map with different compressions: CSV(uncompressed): 47.2kB Base64(uncompressed): 121.2kB Base64(gzip): 2.2kB Base64(zlib): 2.1kB Base64(zstd): 1.9kB

However one of the biggest factors isn't just the size of the file. zstd is known for being faster at decompressing data than gzip and zlib. Which means that import times in godot for the maps are so much faster, especially for really large maps. This saves a lot of development time each time you have to modify a big map or importing many maps at once.