add customization docs

[ks6088ts]

What this PR does / why we need it

adding docs to guide users to customize RAG app

Which issue(s) this PR fixes:

Fixes #100

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

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

How to Test

• Get the code

git clone [email protected]:ks6088ts-labs/workshop-azure-openai.git
cd workshop-azure-openai

• Test the code

make ci-test

What to Check

Verify that the following are valid

• ...

Additional Information