Request: Arbitrary file upload in editor, inserted into transaction comment

[MatthewCroughan]

I would like to be able to upload receipts in-line in the ledger transaction in a comment/tag field, in the same way that GitHub markdown works, i.e when you press ctrl + v it uploads data to GitHub's webserver, and embeds it by-hash in the markdown, like this:

![image](https://github.com/user-attachments/assets/f427652f-60cf-4bdf-bafd-9a3f4d9ed6b2)

The ledger transaction could look like this:

2024/09/04 Mobile
    ; data/e4f79f3d8a95fde15d32d71842ef750040c59dbc4ba9cdd35abc3df417fbd17e.pdf
    Expenses:Utilities                                400 INR
    Liabilities:CreditCard:Freedom

there's only three components to it:

1. The storage location
2. The filename (Ideally computed by hash)
3. The filetype (Ideally inferred from the upload)

If you were feeling fancy, you could even scan all ledger transactions and garbage-collect/remove all files which are no longer referenced by journal entries.

The reason I would like this is so I can get into the habit of linking my transactions to photographic receipt evidence.