Use "uv" for title of index instead of "Introduction" (#5677)

<img width="807" alt="Screenshot 2024-07-31 at 5 12 48 PM"
src="https://github.com/user-attachments/assets/8a3cc824-c242-4688-a7d9-5b88198a6b94">
vs
<img width="807" alt="Screenshot 2024-07-31 at 5 13 21 PM"
src="https://github.com/user-attachments/assets/04f77771-94c3-4d2e-81d2-2db63aa649bd">

docs/index.md

@@ -1,3 +1,5 @@
+# uv
+
 An extremely fast Python package and project manager, written in Rust.
 
 <p align="center">