Update readme.md for which repos to contribute to

[peterdudfield]

Update the readme so that open source contributors can easily see which repos that can help with

We could have the following labels

• Internal OCF code e.g. ocf-infrastructure
• Open Source ML models .e.g Metnet
• Stand alone repos, ready for open source contributors e.g Open Quartz Solar Foreacasting
• other catorgizes?

Another way to label things might just be how easy the code is accessible to open source contributors

• Easy, e.g. Open Quartz Solar Foreacasting
• Medium, e.g. ocf datapipes
• Hard, PVnet

[peterdudfield]

We could put this label as a another column on the current Readme.md

[peterdudfield]

Perhaps a green/orange/red system could be used for how easy it is for people to contribute