Moves quickstart page before installation (#382)

# Description

Moves the quick start guide to before installation pages in the docs.

## Type of change

- This change requires a documentation update

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [ ] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

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docs/index.rst

@@ -77,9 +77,9 @@ Table of Contents
    :caption: Getting Started
 
    source/setup/ecosystem
+   source/setup/quickstart
    source/setup/installation/index
    source/setup/installation/cloud_installation
-   source/setup/quickstart
 
 .. toctree::
    :maxdepth: 3