1. Add ale.setup and ale.setup.buffer for pure Lua configuration.
2. Update many global settings to use Booleans instead of numbers to
make types easiert to work with in Lua.
3. Radically reformat documentation and fix errors to make
documentation more usable for Neovim users.
Nickel(https://nickel-lang.org/) is a configuration language, like
Jsonnet, Cue, Dhall.
`nickel`(https://github.com/tweag/nickel) is the main command to run,
export and also format Nickel code.
this commit adds `nickel format` as a Nickel fixer, together with some
tests and documentation.