Rename tests.lib.path.Path.{abspath -> resolve()}

Explicit support for hg+file

Fix a typo in InstallCommand.__doc__

Add NEWS file for new contextlib2 dependency

Add a good-first-issue template

Bump to latest sphinx

Revert "Remove GitHub Actions CI"

Example: after installing six 1.12.0, `pip install -Uv six==1.12.0`
now returns immediately, instead of going to the index to check for a
version that can’t possibly be considered better.

This optimization is most significant when upgrading via a
requirements file with many pinned versions and some non-pinned
versions.
Signed-off-by: NAnders Kaseorg <andersk@mit.edu>

This is based on Warehouse's template, adapted to use language we
already use in our existing good-first-issues and with clearer
instructions for what's needed in these kinds of issues.

Why: This seems to be causing 500 errors for @pradyunsg on PRs.

https://twitter.com/AndersKaseorg/status/1179851971433385984

Move find_egg_info to operations.generate_metadata

Allow error reporting for YAML tests

Clarify `--no-binary` when enumerating packages and add an example