[Sept Sprint] Gross Store

[iHiD]

This is part of our September Spring to get the Go Track in shape. Please read the Overview issue for more details. This exercise is claimed by @MiroslavGatsanoga .

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• gross-store: tweak introduction #1593
• gross-store: missing prerequisites #1592
• gross-store: exemplar uses unknown syntax #1591

[MiroslavGatsanoga]

I'd like to work on this one :)