fn: add conversions between Result and Option

fn/result_test.go

@@ -1,6 +1,7 @@
 package fn
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -9,3 +10,10 @@ import (
 func TestResultUnwrapOrFail(t *testing.T) {
 	require.Equal(t, Ok(1).UnwrapOrFail(t), 1)
 }
+
+func TestOkToSome(t *testing.T) {
+	require.Equal(t, Ok(1).OkToSome(), Some(1))
+	require.Equal(
+		t, Err[uint8](errors.New("err")).OkToSome(), None[uint8](),
+	)
+}