docs/fiddle: add "incomplete" fiddle.

Change-Id: I66246d6c421cf91b459207d91e4899c4c030e45e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/248159
Reviewed-by: Ben Wagner aka dogben <benjaminwagner@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
2 files changed