Add a weather API client

[leandro-lucarella-frequenz]

What's needed?

We need to provide a weather API client.

Proposed solution

Write a client based on what we have for the microgrid API.

This should live in frequenz.sdk.weather.client to also follow the microgrid API.

Use cases

No response

Alternatives and workarounds

No response

Additional context

Dispatching will be a core part of building actors and apps, so we need to include support for it in the SDK.

FYI @sahas-subramanian-frequenz @thomas-nicolai-frequenz

[llucax]

This is being done as a separate repo.