docs(usage-view): how to use csv data export

[mwasilew2]

Description of the change

related to: https://app.clickup.com/t/8693k73r6

Adds docs about downloading and analyzing usage data.

Checklist

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[render]

Your Render PR Server URL is https://spacelift-user-documentation-pr-438.onrender.com.

Follow its progress at https://dashboard.render.com/static/srv-cmokucv109ks73df26q0.

[mwasilew2]

@flavius-dinu I tagged you cause I saw you did some work on docs before. Let me know if there's someone else I should be asking for review. Thanks!

[jakubdal]

Please wait for run state translation and recreate the image. Also please wait for feature GA before publishing. LGTM overall.

[mwasilew2]

this is ready to be merged when the feature goes GA