infra: source github templates (#1425)

## What

- Adds PR and Issue templates.


## Meta
What do you think about vendoring some of the general things from ruff
and other repos into a `.github` repo. This way one change against a
"generalized template" or config would propagate to all repos in the
org.



Mainly thinking about issue/pr templates and other common [community
health
files](https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/creating-a-default-community-health-file)
([example](https://github.com/litestar-org/.github))

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,10 @@
+<!--
+Thank you for taking the time to report an issue! We're glad to have you involved with uv.
+
+If you're filing a bug report, please consider including the following information:
+
+* A minimal code snippet that reproduces the bug.
+* The command you invoked (e.g., `uv pip sync requirements.txt`), ideally including the `--verbose` flag.
+* The current uv platform.
+* The current uv version (`uv --version`).
+-->

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,15 @@
+<!--
+Thank you for contributing to uv! To help us out with reviewing, please consider the following:
+
+- Does this pull request include a summary of the change? (See below.)
+- Does this pull request include a descriptive title?
+- Does this pull request include references to any relevant issues?
+-->
+
+## Summary
+
+<!-- What's the purpose of the change? What does it do, and why? -->
+
+## Test Plan
+
+<!-- How was it tested? -->