feat: add docopts formula

- docopts does not yet have a Brew formula, so testing creating one with my tap
- see also my issue: docopt/docopts#59

Formula/docopts.rb

@@ -0,0 +1,20 @@
+class Docopts < Formula
+  desc "Shell interpreter for docopt, the command-line interface description language"
+  homepage "https://github.com/docopt/docopts"
+  url "https://github.com/docopt/docopts/archive/v0.6.4-with-no-mangle-double-dash.tar.gz"
+  sha256 "5bf29a4eaa07cb3d1449077697d8746678cc490ee3e63cfe3e1025cebf2f4008"
+  head "https://github.com/docopt/docopts.git", branch: "master"
+  license "MIT"
+
+  depends_on "go" => :build
+
+  def install
+    system "go", "build", "docopts.go"
+    prefix.install_metafiles
+    prefix.install "docopts.sh" # helper functions, meant to be sourced
+  end
+
+  test do
+    assert_match "Shell interface for docopt, the CLI description language.", shell_output("#{bin}/docopts -h")
+  end
+end