docs: docusaurus setup (#3541)

# What does this PR do?

- Docusaurus server setup
- Deprecates Sphinx build pipeline
- Deprecates remaining references to Readthedocs
- MDX compile errors and broken links to be addressed in follow-up PRs

<!-- Provide a short summary of what this PR does and why. Link to relevant issues if applicable. -->

<!-- If resolving an issue, uncomment and update the line below -->

<!-- Closes #[issue-number] -->

## Test Plan

```
npm install
npm gen-api-docs all
npm run build
```

<!-- Describe the tests you ran to verify your changes with result summaries. *Provide clear instructions so the plan can be easily re-executed.* -->

docs/src/components/HomepageFeatures/styles.module.css

@@ -0,0 +1,11 @@
+.features {
+  display: flex;
+  align-items: center;
+  padding: 2rem 0;
+  width: 100%;
+}
+
+.featureSvg {
+  height: 200px;
+  width: 200px;
+}