Upgrade template

[pacrob]

What was wrong?

Merge changes from the project template, notably:

• drop python 3.7
• use pre-commit for linting
• change the name of the master branch to main

Closes #207

eth-abi previously only had typing for the eth_abi/utils folder. This PR adds typing for the eth_abi/tools folder, and adds the remaining files as a list to be excluded from mypy in .pre-commit-config.yaml As typing is added to individual files, those can be removed from the exclude list.

Todo:

• [ ] replace functools.lru_cache - flake8-bugbear rule B019

  • decided this deserves its own PR - Issue #218

• [x] Clean up commit history

• [x] Add or update documentation related to these changes

• [x] Add entry to the release notes

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[fjarri]

It seems that this PR deleted py.typed in the main eth_abi directory, thus breaking type checking in dependencies. Was that intentional?

[pacrob]

@fjarri Sorry about that. I had moved the py.typed to the tools and utils folders because they were fully typed, while the eth_abi/*.py files only have minimal typing. I didn't think about the downstream breaking. I'll get that back in there.

[fjarri]

No problem, just wanted to make sure it wasn't accidental. Technically the change appeared in v5.0 so API breakage is expected. I have no problem with doing some explicit cast() until py.typed can be returned.