docs[install/pre-build binaries]: add runtime setup

[guissalustiano]

Hi!

Context

I installed my helix by pre-build binary following the book, and the highlight didn't work.
I found the issue #1098 with the problem and the solution, and moving the runtime to the correct location the syntax highlight started to work.

What these issue solve?

These issues update the installation of the pre-build binary docs to add the runtime folder information, so people who follow the instructions will have the syntax highlighting working on the first time.

Other possible implementation

The book explains how to setup the runtime folder on the building by the source section, but I didn't find it on the first time because it was too far away and in the build by source section, so I didn't expect do need to follow these steps, but we can also make one session just for the runtime and like both the binary installation and by source to it

[the-mikedavis]

just some small formatting nits

[archseer]

I kind of disagree with this though, it instructs the user to put system files under their user directory. It's also likely the user will forget to update this in the future.

[guissalustiano]

I think we agree that previously, it was also a problem, right?

The user folder is an example that works for most of the users, but I expect that those who need to install it for multiple users will know how to do it in another way.

@archseer do you have some suggestions about how to improve it?

[archseer]

The preferred route should be a symlink since that should be easier to update. But the binary also looks for runtime files co-located with it so it can be used straight away after unzipping

[guissalustiano]

the binary also looks for runtime files

Hmm, I didn't know that, so the docs are not as wrong as I thought.

I still think that it's nice to explain the runtime folder, but we can maybe keep with the binary for the pre-build binary. Does that make sense?