Add missing periods (`.`) to list elements in `Features` docs page (#15138)
The [**Features**](https://docs.astral.sh/uv/getting-started/features/)
page of docs contains a lot of markdown lists, elements of which end
with `.`.
For example:
<img width="571" height="267" alt="image"
src="https://github.com/user-attachments/assets/b485f310-fece-4da4-acb9-ebc68b9df7d3"
/>
---
Out of tens of list elements, just two are outliers and do not use `.`
at the end.
So this small PR fixes this little inconsistency :)