Use YARD for API documentation.

Massive TODO.

We'll get there eventually...

.gitignore

 /*
 !/.gitignore
+!/.yardopts
 !/Library/
 !/CODEOFCONDUCT.md
 !/CONTRIBUTING.md

.yardopts

+--title "Homebrew"
+--main Library/Homebrew/API.md
+Library/Homebrew/**/*.rb
+*.md

Library/Homebrew/.rdoc_options

---- !ruby/object:RDoc::Options
-encoding: UTF-8
-static_path: []
-rdoc_include:
-- .
-charset: UTF-8
-exclude:
-hyperlink_all: false
-line_numbers: true
-main_page:
-markup: rdoc
-page_dir:
-show_hash: false
-tab_width: 2
-title: Homebrew
-visibility: :protected
-webcvs:

Library/Homebrew/API.md

+# Homebrew Public API
+We're (finally) working on a documented public API for Homebrew. It's currently a work in progress; a bunch of public stuff is documented and a bunch of private stuff is undocumented. Sorry about that!
+
+The main class you should look at is {Formula}. Assume everything else is private for now.