Promote uv in installation guides (#14056)

> [Because this is an Astral repository
;)](astral-sh/packse#183)

[Originally
reported](https://discord.com/channels/1039017663004942429/1039017663512449056/1302319421204729906)
by clearfram3 on Discord.

`grep`ping for `pip install` in `.md` files reveals a few other places
where the same fix might be applicable.

---------

Co-authored-by: Micha Reiser <micha@reiser.io>

README.md

@@ -119,6 +119,10 @@ For more, see the [documentation](https://docs.astral.sh/ruff/).
 Ruff is available as [`ruff`](https://pypi.org/project/ruff/) on PyPI:
 
 ```shell
+# With uv.
+uv add --dev ruff     # to add ruff to your project
+uv tool install ruff  # to install ruff globally
+
 # With pip.
 pip install ruff
 

docs/faq.md

@@ -223,6 +223,11 @@ Ruff is installable under any Python version from 3.7 onwards.
 Nope! Ruff is available as [`ruff`](https://pypi.org/project/ruff/) on PyPI:
 
 ```console
+# With uv.
+$ uv add --dev ruff     # to add ruff to your project
+$ uv tool install ruff  # to install ruff globally
+
+# With pip
 $ pip install ruff
 ```