Add "Google Chrome" cask

Added the google-chrome (1) cask which is used for web development to
use DevTool (2) features only available in Chrome (e.g. Lighthouse) and
to test and compare possible browser differences.

References:

  (1) https://github.com/Homebrew/homebrew-cask/blob/master/Casks/google-chrome.rb
  (2) https://developers.google.com/web/tools/chrome-devtools

Closes GH-148

snowflakes/homebrew/Brewfile

@@ -164,6 +164,7 @@ cask "font-twitter-color-emoji"
 cask "font-varela-round"
 cask "gdisk"
 cask "gimp"
+cask "google-chrome"
 cask "hwsensors"
 cask "iina"
 cask "insomnia"