Add sketch describing data flow and management (closes #107)

[LakshithadeSilva]

closes #107
Add a sketch describing the data flow between the key data storage elements and their layout in a FRIDGE.

[JimMadge]

Having the figure's source is useful, but it isn't an image we can use in docs.
Can you tag your PRs with "closes #" or "fixes #" if it should close an issue, otherwise the automation doesn't work.

We should make sure this connects with the documentation work in #105 and #124.

@LakshithadeSilva @craddm @jakewatson-bristol Let's make sure these connect and close these PRs.
Something like Markdown in a /docs directory is fine for now, we can worry about the document engine later.

[JimMadge]

There are docs in main now. Let's put this in an architecture section.

I think we shouldn't remove the newline from the end of the file if excalidraw is going to add it back in if we make any changes.
Should be able to ignore these files in pre-commit.

[LakshithadeSilva]

Rebased on main and moved the MinIO sketch to a new folder called 'architecture' within docs.