Add sample for OCI context with base image trigger

[sajayantony]

Purpose

Add a sample to show how to use an OCI context.

• ...

Does this introduce a breaking change?

[ ] Yes
[X] No

Pull Request Type

What kind of change does this Pull Request introduce?
Documentation changes and sample with azure cli commands.

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[X] Documentation content changes
[ ] Other... Please describe:

[estebanreyl]

Could we maybe add a note on when using this might be beneficial. As far as I can tell this is the first mention of using an OCI context in our docs so it might be good to give some additional guidance and context to users