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/options.html b/src/options.html
index 8bb4fb2..b571a8c 100644
--- a/src/options.html
+++ b/src/options.html
@@ -21,6 +21,7 @@
         <input type="checkbox" id="increasecontrast"> <label for="increasecontrast" data-i18n="increasecontrast"></label><br>
         <input type="checkbox" id="stickysidebarheaders"> <label for="stickysidebarheaders" data-i18n="stickysidebarheaders"></label><br>
         <input type="checkbox" id="ccdarktheme"> <label for="ccdarktheme" data-i18n="ccdarktheme"></label> <span class="experimental-label" data-i18n="experimental_label"></span><br>
+        <input type="checkbox" id="ccforcehidedrawer"> <label for="ccforcehidedrawer" data-i18n="ccforcehidedrawer"></label><br>
       </p>
       <h4 data-i18n="profileindicator_header"></h4>
       <p>