Add support for sha348

[Firesphere]

Is your feature request related to a problem? Please describe

Composer provides a sha348 of the build, but I can't validate it directly in pyinfra, because it doesn't have a sha348 method.

Describe the solution you'd like

Add a sha348 validation for files.download(). Optionally, probably cleaner, a way to give a specific hashing algorithm, e.g.
files.download('https://example.com/download.file', hash=abcxyz123, algorithm=sha512), or similar

[simonhammes]

Good suggestion, I'll propose a PR :)