Add ChromeOS support

Adds CrOS to defaultPlatform frontmatter, as Linux.

Author: sirocyl

javascripts/display-platform-specific-content.js

@@ -12,6 +12,7 @@ export default function displayPlatformSpecificContent () {
   if (platform === 'darwin') platform = 'mac'
   if (platform === 'ios') platform = 'mac'
   if (platform === 'android') platform = 'linux'
+  if (platform === 'cros') platform = 'linux'
   if (platform.startsWith('win')) platform = 'windows'
 
   const platformsInContent = findPlatformSpecificContent(platform)

javascripts/user-agent.js

@@ -6,6 +6,7 @@ const OS_REGEXPS = [
   /(mac) os x ([^);]+)/i,
   /(windows) ([^);]+)/i,
   /(android) ([^);]+)/i,
+  /(cros) ([^);]+)/i,
   /(linux) ([^);]+)/i
 ]