Unfortunately there's no easy way to share this code with the brew.sh
site but it's at least able to have the `css/`, `img/` (root) and
`_layouts` directories in sync between the two repositories.

Some small CSS tweaks were needed to make these pages render more
attractively.

Closes #2186.

Also update command specifications to match descriptions.

Fixes to spelling and punctuation for consistency and readability.

Bare URLs are auto-linked on GitHub but not on docs.brew.sh, so I added
angle brackets around them where appropriate. Also converted
Markdown-linked URLs for clarity.

As requested in https://github.com/Homebrew/homebrew-core/issues/9316.

The "Messaging" heading was failing to be rendered due to a missing newline between it and "Convenience Tools".

This is used to indicate a formula is a version of another formula.
This will be used to provide a consistent interface for older formulae
versions and replaces the use of `conflicts_with`.

These can now be done with just `brew upgrade`, like other upgrades.

Fixes #1818.

resolves https://github.com/Homebrew/brew/issues/1821

There are some formulas in which Homebrew symlinks configuration files
into /usr/local/etc/ instead of copying them, resulting in custom
settings being overwritten on package upgrades. This addition to the
documentation illustrates one way to avoid this behavior by ensuring the
configure script is told where to copy the configuration file(s).

Refs https://github.com/Homebrew/homebrew-core/issues/8711

Fixes #1817.

Unfortunately `brew linkapps` cannot behave nicely with e.g. Spotlight
using either aliases or symlinks and Homebrew formulae do not build
"proper" `.app` bundles that can be relocated. Instead, please consider
using `brew cask` and migrate formulae using `.app`s to casks.

GitHub now nicely generates a documentation site for us at
http://brew.sh/brew based on our docs folder. Optimise the output of
this and the GitHub docs directory for readability and the various user
groupings.

Mostly related to the newer ways we’re handling versions and the
incoming deprecation of devel-only, head-only and versions.

When reproducing issues with software that hasn’t been bottled yet on
your version of macOS it can sometimes be helpful to use `or_later`
bottle functionality i.e. just use the bottle for the latest version of
macOS available. This maps well to the existing `--force-bottle`
argument so it will now act as if the latest bottle has a `or_later`
ending.

meson is quickly gaining popularity as build system, in combination with
ninja. Several Gnome projects for example are currently transitioning
from autotools to meson, mostly because it allows for Visual Studio
builds, which is impossible to accomplish with autotools.

In order to facilitate generating meson based Formulas, I added support
for meson to brew-create.