chore(docs): update TOC

Author: YertleTurtleGit

README.md

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 Performs Principal Component Analysis (PCA) with optional graph distance for neighborhood composition.
 
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+**Table of Contents**
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+- [Geodesic Graph Distance](#geodesic-graph-distance)
+  - [Why?](#why)
+  - [What?](#what)
+  - [Results](#results)
+  - [Why not?](#why-not)
+- [Installation](#installation)
+- [Example](#example)
+  - [Classic PCA](#classic-pca)
+  - [Graph PCA](#graph-pca)
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 # Geodesic Graph Distance