Add ttl example

[kennethmhc]

No description provided.

[aversey]

Some changes are to be made. Overall, I don't think the structure of "a bunch of examples" works well here. There is clearly a single main example and then a bit of information on how to update a TTL value of an existing FG. The main example itself is also too abstract to be relatable; it is better to use a concrete, simple FG instead. I would also try to summarize the goal of TTL usage in the example (to save resources or to simplify the usage of the FG) and state that it is achieved by following the guide/example. A user guide should show a user exactly how to achieve something useful for them; for easier searching, the useful effect of the guide should be stated explicitly.

[kennethmhc]

The original intend is to create example for TTL as requested by Ray. But I can extend it to include the use cases.