[tech] Integrity checks for Gemini pages

[Almaember]

Hello, everybody!

I know that there is no way in Gemini right now to check the integrity 
of pages. However, it would be nice for this to possible.

I think this feature is pretty much required for the protocol to be 
taken seriously, but that's just my opinion

Of course, it would be the best to do this in a way that doesn't break 
existing implementations. My ideas are:

a) A file in the same directory as the downloaded file, but with 
.integrity added at the end,
containing a hash as "<algorithm>:<hash-in-hex>".
This is definitely compatible with all existing clients, but it breaks a 
lot of the conventions of Gemini, such as the one-file-per-page rule.

b) Add a new MIME-type parameter, let's call it "integrity" again, that 
contains the has in the same format as option a.

It's possible that this would be pointless, so if it is let me know. 
This is just an idea to, for example, allow the downloading of larger 
files properly.

Cheers,
~almaember