(Feature request): Sources for suitable time-series data

[khalida]

Hi, this is a feature request not a bug-report.

I thought it might be useful to collate a list of links to useful data-sources for relevant time-series data which is publically available for different networks around the world. I was thinking we could maintain a collaborative list - which might help save duplicated effort, and also allow more easy comparison of value propositions on different networks.

If this would be of interest, I'd be happy to start a list - and add links to the NGESO (GB grid) data sources. I'm not sure what the most convenient format would be? Perhaps just another Markdown file which is pointed to from the main README.md?