Add 'always hide CC drawer' option

When the CC starts up, it opens the drawer by default. The option
introduced by this commit closes it as soon as the content script gets
injected into the page.

Feature suggested at pekb/thread/67965396?msgid=69642485

Fixes: #10
Change-Id: I2a043dc9888eee2c9b1f98713d36cd1a49d3c931
diff --git a/src/_locales/en/messages.json b/src/_locales/en/messages.json
index d542386..3472ee8 100644
--- a/src/_locales/en/messages.json
+++ b/src/_locales/en/messages.json
@@ -79,6 +79,10 @@
     "message": "by the OS dark mode setting",
     "description": "Select option added in #ccdarktheme_mode--container, in the options_ccdarktheme string"
+  "options_ccforcehidedrawer": {
+    "message": "Always hide the drawer (left column) in the Community Console.",
+    "description": "Feature checkbox in the options page"
+  },
   "options_profileindicator_header": {
     "message": "Indicator dot",
     "description": "Heading for the profile indicator feature options"