Add files for pre-commit configuration (pylint and black)

[antalszava]

Context:

The pre-commit package allows installing git pre-commit hooks. Such a hook refers to running dedicated tools (e.g., pylint and black) each time a developer issues the git commit command locally. If the run for one of the tools fails, then committing fails too. The hook for black automatically applies black.

Description of the Change:

Adds a

• .pre-commit-config.yaml top level file
• pyproject.toml top level file

Extends the documentation of creating a pull request to mention the use of pre-commit.

Benefits:

An easy and standardized way of configuring git pre-commit hooks for PennyLane developers.

Possible Drawbacks:

As noted in the docs entry, as new versions of black are being released, pre-commit autoupdate may have to be reissued because pre-commit installs packages

Related GitHub Issues:
N/A

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit doc/releases/changelog-dev.md with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.

[codecov]

Codecov Report

Merging #2567 (9e2039f) into master (6892a0c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2567   +/-   ##
=======================================
  Coverage   99.58%   99.58%           
=======================================
  Files         243      243           
  Lines       19595    19595           
=======================================
  Hits        19514    19514           
  Misses         81       81           

---

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[antalszava]

[sc-19544]

[albi3ro]

@antalszava When I ran pre-commit run --all-files locally, it also styled:

reformatted doc/_static/style/style_examples.py
reformatted doc/_static/draw_mpl/draw_mpl_examples.py
reformatted doc/_static/tape_mpl/tape_mpl_examples.py
reformatted doc/conf.py
reformatted doc/_static/drawer/mpldrawer_examples.py

I personally see no problem with those files being styled as well, but the regular expression in pyproject.toml may need changing if we want to limit it to pennylane and tests.

[rmoyard]

It looks all good, I've added some suggestions. Same as @albi3ro, if I run the all file options, the docs are included and I have both pylint and black errors. Is it possible to change the definition of all files in the config?

[antalszava]

Thank you @albi3ro and @rmoyard for the catch and the comments! I've updated the exclude patterns and extended the description in the docs.

[rmoyard]

@antalszava Thank you, it looks all good 💯