Add LogWriter

Sources/ElixxirDAppsSDK/LogWriter.swift

+import Bindings
+import XCTestDynamicOverlay
+
+public struct LogWriter {
+  public init(handle: @escaping (String) -> Void) {
+    self.handle = handle
+  }
+
+  public var handle: (String) -> Void
+}
+
+extension LogWriter {
+  public static let unimplemented = LogWriter(
+    handle: XCTUnimplemented("\(Self.self)")
+  )
+}
+
+extension LogWriter {
+  func makeBindingsLogWriter() -> BindingsLogWriterProtocol {
+    class Writer: NSObject, BindingsLogWriterProtocol {
+      init(_ writer: LogWriter) {
+        self.writer = writer
+      }
+
+      let writer: LogWriter
+
+      func log(_ p0: String?) {
+        guard let p0 = p0 else {
+          fatalError("BindingsLogWriter.log received `nil`")
+        }
+        writer.handle(p0)
+      }
+    }
+
+    return Writer(self)
+  }
+}