docs: add installation and build guides from wiki to repo

[dundargoc]

No description provided.

[clason]

We should also update the links in

1. README.md
2. Wiki Home.md

[wookayin]

How about having a top-level docs/ folder?

EDIT: NVM, if we are not moving all the docs from wiki but only build/installation instructions, I think it will be enough.

[clason]

Yes, these two files are special since they are mainly useful before you have built and/or installed Neovim. For everything else, the goal is to move that into actual (vimdoc) help documents eventually (after pruning/updating), or offload to neovim.io.

(Also, welcome to the team! 🥳 )

[clason]

Possible follow-ups (note for future reference):

• move https://github.com/neovim/neovim/wiki/FAQ to faq.txt
• move https://github.com/neovim/neovim/wiki/Merging-patches-from-upstream-Vim (dev-vim-patches.txt? or merge with MAINTAIN.md/CONTRIBUTING.md?)

[justinmk]

these two files are special since they are mainly useful before you have built and/or installed Neovim

Can we also put these in runtime/doc/ :) Because the website needs an "Install" page, and might as well also give it a "Build" page. The README can link to the runtime/doc/*.txt files using relative paths so there isn't really a discoverability issue there.

Of course we could have a special-purpose "Install" page on the website, but I'd rather focus on perfecting one page instead of multiple pages. It also drives improvements to :help, such as URL rendering, images, etc.

[clason]

They're quite heavy on the links, though, which would make them significantly harder to navigate after pushing them through the gen_html_help sausage grinder... So I'd consider those help improvements to be a blocker for the move. (I've looked into reference link parsing for vimdoc and maybe using OSC8, but it's not trivial.)

INSTALLING and BUILDING are also typical files in a source repo, so much more visible to people coming here.

So I'd prefer to leave them here, at least for now; this round of cleaning is not the last round -- after we've cleaned out the Wiki, the next step will be consolidating (and moving) all the various markdown files.

[justinmk]

Fair enough.

[dundargoc]

Personally I don't mind either way, except that I want this done speedily so the information isn't fragmented in two repos for long. Let's move forward with this for now so we can clean up the wiki and we can deliberate more on how to best present this information later.