Idea: add hashes in generated .lock file

[dmerejkowsky]

Since version 8, pip can now process requirements.txt files and check their hashes after download.

https://pip.pypa.io/en/stable/reference/pip_install/#hash-checking-mode

I think it would be a good idea to store those hashes in the generated .lock file

(A big inconvenience af the hash-checking mode of pip is that you have to specify the hash for every package and their dependencies, recursively ...)

[kennethreitz]

Already there!