added docs

doc.go

@@ -2,6 +2,42 @@
 Package opt has a number of sub-packages provides alternatives to Go's built-in types (bool, float64, int64, string, time.Time)
 that also let you express a "lack of a value"; for the Go programming language; these are similar to "option types" or "maybe types"
 in some other programming languages.
+
+Example:
+
+	var s optstring.NullableType
+	
+	// ...
+	
+	switch s {
+	case optstring.NoneNullable():
+		//@TODO
+	case optstring.Null():
+		//@TODO
+	case optstring.SomeNullable("Hello world!"):
+		//@TODO
+	case optstring.SomeNullable("apple banana cherry"):
+		//@TODO
+	default:
+		//@TODO
+	}
+
+Example:
+
+	var s optstring.Type
+	
+	// ...
+	
+	switch s {
+	case optstring.None():
+		//@TODO
+	case optstring.Some("Hello world!"):
+		//@TODO
+	case optstring.Some("apple banana cherry"):
+		//@TODO
+	default:
+		//@TODO
+	}
 */
 package opt