Add type hints for Spond and SpondClub __init__() methods.

[elliot-100]

This is a key 'missing piece' that should enable static type-checkers (e.g. mypy or IDE tools) to analyse the code fully, and help resolve more complex issues.

[elliot-100]

I've gone ahead and merged this one @Olen, as it has no run-time impact, and as type hints aren't enforced, is really just a form of documentation. Hope that's OK.

[Olen]

I fully trust your judgement on all of these, @elliot-100

With a community it seems like this is building right now, I hope more eyes will catch more errors.
I very much want to participate, and especially in the more high level discussions or bigger changes, but for me it is fine to do cleanups, corrections, clarifications etc. without waiting for my approval.