Add type hints to nissan_leaf integration

[filcole]

Proposed change

Use type hints for nissan_leaf component. I'm new to python typing so improvements gratefully accepted!

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• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
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[chemelli74]

Hi @filcole, thx for your contribution!

To fully enable strict typing please consider also to:

1. add nissan_leaf to .strict-typing file
2. run "python3 -m script.hassfest"
3. run "mypy homeassistant/components/nissan_leaf"

Simone

[filcole]

Thanks @chemelli74 - really helpful, adding to .strict-typing makes mypy much more helpful.

[frenck]

Thanks, @filcole 👍