feat(workflow): add workflow to handle stale issues and PR

[CunliangGeng]

Description

Related to issue #324 .
Add gh action to check and close stale issues and PRs.

With current setting, the action runs at midnight of every Mon., Wed. and Friday.
If an issue has no no activity for 30 days after creating, it'll be labeled as stale; if no activity for 7 days after marking stale, it'll be closed.
For a PR, it's 14 days for labelling stale and 7 days for closing it.

It uses this gh action https://github.com/actions/stale

Instructions to review the pull request

Create a python-template-test repo on GitHub (will be overwritten if existing)

cd $(mktemp -d --tmpdir py-tmpl-XXXXXX)
cookiecutter -c <pr-branch> https://github.com/<pr-user>/python-template
# Fill with python-template-test info
cd python-template-test
git init
git add --all
git commit -m "First commit"
git remote add origin https://github.com/<you>/python-template-test
git push -u origin main -f
python -m venv env
source env/bin/activate
python -m pip install --upgrade pip setuptools
python -m pip install '.[dev,publishing]'

[fdiblen]

Hi @CunliangGeng,

Thank you for the suggestion. I cannot find a related issue which this PR solves. Would you please have a look at https://github.com/NLeSC/python-template/blob/main/CONTRIBUTING.md before creating a PR?

[CunliangGeng]

Thanks for the reminder. I created issue #324 for this PR :-) Have a look please.