Add a knowledge.google.setApiKey function

[ben-pr-p]

By requiring an environment variable, you're limiting the end users configuration options and potentially forcing them to rename other google API keys that they don't want to conflict.

Easiest solution would be to have a knowledge.google.setApiKey(apiKey) function that set the API key, and fallback to GOOGLE_API_KEY otherwise.

If you agree, I'll be happy to submit the PR!

[mycaule]

Thanks for the feedback, I'll have a look and will clean the repo this Christmas holiday (update dependencies, see if I can make quick wins..).

I haven't been in this repo for a while, I didn't notice there were a few users.

If you want to do a PR I will review it. Thanks.