community tools: Neovim guide from Practicalli

[practicalli-johnny]

Add install guide section to Neovim and include link to Practicalli Neovim

Update link to Practicalli guide to spacemacs

• [x] Have you read the guidelines for contributing?
• [x] Have you signed the Clojure Contributor Agreement?
• [x] Have you verified your asciidoc markup is correct?

[puredanger]

note that we are in the midst of migrating the web site, so while I will merge, it won't show up for the moment, but we're cutting over soon.