Add pre-commit config

[kenodegard]

Description

This is mostly just a copy from https://github.com/conda/conda/blob/main/.pre-commit-config.yaml.

Autofixing is explicitly disabled:

conda-content-trust/.pre-commit-config.yaml

Lines 1 to 3 in 181a70f

	# disable autofixing PRs, commenting "pre-commit.ci autofix" on a pull request triggers a autofix
	ci:
	autofix_prs: false

This adds pre-commit checks for:

1. mixed-line-ending
2. end-of-file-fixer
3. trailing-whitespace
4. check-toml
5. check-yaml
6. check-json
7. check-merge-conflict
8. fix-encoding-pragma
9. darker
10. blacken-docs
11. flake8

    Note
    Results are ignored (see --exit-zero)

12. pylint

    Note
    Results are ignored (see --exit-zero)

13. bandit

    Note
    Results are ignored (see --exit-zero)

14. insert-license

Once this is ready to merge we will need to enable the pre-commit CI bot (see checklist below).

Supersedes #34

Checklist - did you ...

• Add a file to the news directory (using the template) for the next release's release notes?
• Add / update necessary tests?
• Add / update outdated documentation?

[kenodegard]

@awwad let's merge this so pre-commit can be installed locally and run as part of git commit hooks, we will postpone enabling pre-commit CI