Added missing documentation to the source code in the Playdate bindings target.

Sources/PlaydateKit/Playdate/Structures/PlaydateError.swift

@@ -1,11 +1,15 @@
 /// An error reported by the Playdate OS.
 public struct PlaydateError: Swift.Error, Sendable {
+    /// The message reported by the OS, or a description of the failure.
     public let message: String
 
+    /// Creates an error with the given message.
     init(message: String) {
         self.message = message
     }
 
+    /// Creates an error by copying an OS-provided C string; a nil pointer
+    /// produces "unknown error".
     init(cString: UnsafePointer<CChar>?) {
         self.init(message: String(playdateCString: cString) ?? "unknown error")
     }