General cleanup and format code with black

[LilSpazJoekp]

About this pull request

This cleans up a few things in the codebase.

Changes

• Moved __version__ and BASE constants to discord_slash/const.py for easier access when they need changed
• Removed non-project patterns that should be placed in a global ignore file from .gitignore
• Removed unused imports
• setup.py
  • Optimized imports
  • Moved requirements into setup.py file since there are now extra requirements only needed when linting or building docs
  • Version info is now parsed from const.py
  • Modified how README.md and const.py are accessed to prevent issues in rare instances
  • Added more pypi classifiers
  • Added license parameter to setup call
• docs
  • conf.py
    • Added version and release info
    • Removed necessary exclude patterns
• Added pre_push.py that will format and lint code automatically for contributors
• Added GitHub Actions for enforcing code style
• Added step for running pre_push.py in pull request template
• Fixed two tiny errors that were uncovered from linting:
  • This needs to be a raw docstring: https://github.com/eunwoo1104/discord-py-slash-command/blob/d5cba045a60aa5f9e3e16d16e7a4520fbdd31e3c/discord_slash/http.py#L115-L125
  • This can be rewritten to use isinstance as suggested by flake8: https://github.com/eunwoo1104/discord-py-slash-command/blob/d5cba045a60aa5f9e3e16d16e7a4520fbdd31e3c/discord_slash/utils/manage_commands.py#L217
• Sorted imports with isort
• Formats code with the tool black

Checklist

• I've run the pre_push.py script to format and lint code.
• I've checked this pull request runs on Python 3.6.X.
• This fixes something in Issues.
  • Issue:
• This adds something new.
• There is/are breaking change(s).
• (If required) Relevant documentation has been updated/added.
• This is not a code change. (README, docs, etc.)

[quirky-bluejay]

@LilSpazJoekp new changes need to be merged 🙂
Also what's the reasoning for ci linting on three os's?

[LilSpazJoekp]

Will do. Since pre_push.py can be ran on those three OSs, it would catch any issues people would have running that.

[LilSpazJoekp]

This is ready now.

[LilSpazJoekp]

You will have to ignore CI errors because the doc strings in components isn't valid reStructuredText.