repro: add multi-cmd example

[jorgeorpinel]

The basics of the multi-cmd feature is already applied to repro in #1980 but we also need a clear example, I think.

[efiop]

That PR is unrelated, you probably meant treeverse/dvc#4934 or #1980 for docs

[jorgeorpinel]

Ah OK yes I was confused. Removed that link, thanks!