Add rag basic tutuorials

[ajithvcoder]

What does this PR do?

Added basic rag tutorial in a generic manner with adalflow
Fixes #194

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• Did you write any new necessary tests? (not for typos and docs) not needed
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• Did you list all the breaking changes introduced by this pull request? No breaking changes

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[fm1320]

Looks good @ajithvcoder , are you able to add an .rst file in the docs linking the relevant notebooks and code and maybe writing a short description about the tutorials ? Similar to the example of docs/source/use_cases/classification.rst.

Doesn't have to be a big explanation, we just want to have an .rst file that accompanies the code whenever possible.

[ajithvcoder]

Sure will do