docs: add documentation for resource CRUD lifecycle via Backstage

[richcooper95]

Users of the SKE Backstage plugins can manage the resource lifecycle via Backstage, but this isn't documented in https://docs.kratix.io/ske/backstage.

We should add documentation for CRUD operations on resources via Backstage (for Anne persona):

• creating a resource (via a Template)
• retrieving the resource (looking at the resource entity page)
• updating the resource (Manage tab)
• deleting the resource (Manage tab)

Users without the ske-backstage-generator will need to have manually generated their Components, including setting all relevant annotations. This is documented already, so this ticket is not blocked on releasing the ske-backstage-generator to customers.

[catmo-syntasso]

Wait until someone asks us for this