docs: add blog post about using Keptn within Argo Workflows

[bacherfl]

Closes #3397

[bacherfl]

I do like this! Very nice structure with clear explanations. I would like to see the AnalysisDefinition introduce the more advanced capabilities of the Analysis feature, just to whet the reader's interest in this very powerful feature.

A few wordsmithing nits, of course. And do you know why readthedocs is apparently not rendering this blog?

thanks for the review and suggestions! I just checked the preview again and it seems like it does show up now

[sonarqubecloud[bot]]

Quality Gate passed

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