Update README.md

[stefanodallapalma]

Made sections with more than 5 entries collapsible to ease user navigation on the markdown. Below an example:

MLOps Core

Click to expand!

1. [Machine Learning Operations: You Design It, You Train It, You Run It!](https://ml-ops.org/) 1. [MLOps SIG Specification](https://github.com/tdcox/mlops-roadmap/blob/master/MLOpsRoadmap2020.md) 1. [ML in Production](http://mlinproduction.com/) 1. ...

[visenger]

Great! @stefanodallapalma - I love the idea!