Add examples to Channel Configuration Timestamping section

[stackedsax]

I noticed a conversation on our internal Slack workspace suggesting that the team would like to see the documentation for timestamps in the Channel Configuration docs improved:

• https://github.com/real-logic/aeron/wiki/Channel-Configuration#timestamps

The team generally had to resort to looking at thee regression tests to understand how things worked:

• https://github.com/real-logic/aeron/search?q=channel-rcv-ts-offset

There was a suggestion to have at least an example or two so we don't have to reverse engineer things.

The docs do have a few improvements since our team mentioned this, but no examples and I bet the subject could do with even more explanation.

[tmontgomery]

Thanks, @stackedsax. We will take a look and see what can be improved.

[mikeb01]

I've added a code sample to that section of the documentation.