[Docs] Fix typos, improve, update at Get Started page (#5587)
* Fix typos, improve, update
* Update _toctree.yml
* Update docs/README.md
Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>
* Update docs/README.md
Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>
* Apply Grammarly fixes
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Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>