Add system requirements to README

[Mr0grog]

This adds a short paragraph about system requirements to the “install” section of the README (that seemed like the most applicable place). While writing this, I wondered if it might make sense to add a paragraph about disk space:

You should also make sure to have about 1.3x the disk space as the amount of data you’d like to be able to store — IPFS takes up a little bit of extra space keeping metadata about your files and about peers on the network. You can also choose different ways to store your data, which will impact the amount of storage space required.

…but I wasn’t sure if that was actually necessary to say or even very accurate (There’s definitely a lot of fudge factor here, and I’m not even sure the 1.3x number is even a great reasonable approximation), so I left it out. I can add it in if people think it’s useful, though.

Fixes #5136.

[Stebalien]

…but I wasn’t sure if that was actually necessary to say or even very accurate (There’s definitely a lot of fudge factor here, and I’m not even sure the 1.3x number is even a great reasonable approximation), so I left it out. I can add it in if people think it’s useful, though.

So, IPFS actually tends to use less space, but that really depends on what you're storing. I'd just say that IPFS may use more or less space, depending on what you're storing.

[Mr0grog]

Sounds like I should just leave it out (i.e. leave the PR as-is) then.