Improve `README` since `dvclive` becomes more important

[shcheklein]

Since dvclive becomes more and more an entry point to the ecosystem I think it worth mentioning/show-casing Studio / VS Code and may be even some basic quick start / templates / example repos.

[daavoo]

templates / example repos.

I think this is worth having a separate issue beyond the README

[daavoo]

I will start by adding the Quickstart in #528 to a Colab notebook

[daavoo]

I will start by adding the Quickstart in #528 to a Colab notebook

Added a little more realistic example (adapted from vscode-dvc-demo) in #530