Fix order of tutorial pipelines

[htahir1]

In the new widget with the 10 pipelines, currently there is no "order" as such. Therefore, I propose, we change the summary.md files in the github folder, to a summary.json that the frontend has to parse. The summary json will have two fields, "description" and "index", where index will be the order in whcih it should be shown on the dashboard.

I have an open PR for this in the tutorial extension repo. Happy to switch this over whenever @Cahllagerfeld is ready: zenml-io/vscode-tutorial-extension#13

[Cahllagerfeld]

closed with #778