Expand on Capability configuration required for account linking

[sisyphusSmiling]

Description

A recent question in Discord reveals a lack of docs coverage on configuring child account NFT collections for access from a parent account. This same question has been raised at least one other time in Discord.

The two account linking guides should be updated with a section or a callout covering the use of Capabilities. A dropdown section and diagram with an explainer on how Capabilities are leveraged to facilitate accessing assets from child accounts would also be helpful for conceptual understanding.

Guidance should cover the fact that child account collections should be configured to include the issuance of a Capability ( e.g. auth(NonFungibleToken.Withdraw) &{ExampleNFT.ExampleNFTCollectionPublic, NonFungibleToken.CollectionPublic, NonFungibleToken.Provider} as shown here) so a CapabilityController can be accessed via the parent account.

It should also be noted that this Capability should not be published, simply issued during setup. An explicit reference to the error they might encounter if they don't complete this step would also be helpful - [Error Code: 1101] cadence runtime error: Execution failed: error: panic: no controller found for capType.