Add a docs page for storage controller

[jcsp]

Problem

External contributors need information on how to use the storage controller.

Summary of changes

• Background content on what the storage controller is.
• Deployment information on how to use it.

This is not super-detailed, but should be enough for a well motivated third party to get started, with an occasional peek at the code.

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[github-actions]

2766 tests run: 2648 passed, 0 failed, 118 skipped (full report)

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Code coverage* (full report)

• functions: 28.0% (6430 of 22994 functions)
• lines: 46.6% (45226 of 97023 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
15b9703 at 2024-04-18T13:53:25.440Z :recycle:}