Terminate ruff when it times out

[Danipulok]

Closes #72.

What

ruff_check calls Popen.communicate(..., timeout=10) with no try around it.
The stdlib does not kill the child when that timeout fires, so a ruff process
that hangs is left running and its stdout and stderr pipes are never closed.
The call now kills the process and waits for it before letting the
TimeoutExpired propagate, so the error a caller sees is unchanged.

Measured on a child that sleeps for 30 seconds against a 0.5 second timeout:

after	poll()	stdin	stdout	stderr
TimeoutExpired	None	closed	open	open
kill() and a second communicate()	-9	closed	closed	closed

That second row is why there is no with Popen(...) block: the second
communicate() already closes every pipe, so wrapping the call would reindent
the whole function and change nothing else.

How to test

make test.

test_ruff_timeout_kills_the_process replaces Popen in pytest_examples.lint
with a subclass whose first communicate raises TimeoutExpired and whose
second delegates to the parent, so the child is a real ruff process and the
kill is real. Without the fix it fails on assert ruff_process.poll() is not None.

[Danipulok]

Hey @samuelcolvin!

I'm really sorry for pinging you if it's inappropriate
I've create some simple PRs and have plans for more (including reading config parts from pyproject.toml)

Would you or someone else be able to check them?
I've tried to make them as simple as possible for the beginning