Sideloading tutorial

[sgwilym]

Adds a tutorial for sideloading. Create a store, create a drop of an area of that store, ingest the drop, everybody's happy.

[AljoschaMeyer]

Store tutorial has broken refs in its summary (the second one should definitely not be broken anymore with this PR):

[AljoschaMeyer]

I think the sideloading tutorial would benefit a lot from a quick refresher of what is going on. A link to the sideloading spec, an reminder of what a "drop" is again (in particular because Drop and drop have preestablished meaning in Rust).

[AljoschaMeyer]

Likewise, Instantiated the export store can be confusing I think: what is an "export store"? Why do we need two stores? What is going on?

[AljoschaMeyer]

I genuinely got confused by this for a second. What are the "contents" of a drop, to be "stored" in a vec? My mind went to a vec of entries first.
(The code block has a similarly confusing comment: // Create a drop and place its contents in a Vec<u8>)

[AljoschaMeyer]

TODO: NICE ENTRY PRINTING!: :#? formatting is probably good enough maybe? I think it might be fine to cheat and manually adjust the purported console output, putting all crypto bytes into a single line but leaving the nice formatting of struct-field-per-line.

[AljoschaMeyer]

typo
(also, is "instantiated" really better than "created"?)

[sgwilym]

Thank you! Tried to address all of these except the pretty printing, lmk what you think.

[AljoschaMeyer]

lgtm now