On Windows, if key is not valid WTF-8,
then error.InvalidWtf8 is returned.
See also:
createMapcontainsConstantcontainsUnemptypub fn contains(environ: Environ, gpa: Allocator, key: []const u8) ContainsError!bool
pub fn contains(environ: Environ, gpa: Allocator, key: []const u8) ContainsError!bool {
if (native_os == .windows and !unicode.wtf8ValidateSlice(key)) return error.InvalidWtf8;
var map = try createMap(environ, gpa);
defer map.deinit();
return map.contains(key);
}