Improve Laplace Demo Notebook and add minimal README

[SauravMaheshkar]

Description

This PR is related to #312. Changes are minimal such as "beautification" of the Notebook by adding a TOC at the top, making some LaTeX equations bigger to make them more readable, deleting redundant code cells. I've also added a minimal README.md within the examples/laplace_demo/ dir.

Checklist

• [x] I have followed the Contribution Guidelines and Code of Conduct
• [x] I have commented my code following the OpenMined Styleguide
• [ ] I have labeled this PR with the relevant Type labels
• [x] My changes are covered by tests

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[SauravMaheshkar]

Request for Review @chinmayshah99

[SauravMaheshkar]

@chinmayshah99 I've updated the conclusion section in da7990e. LMK if it looks okay.