FAB-385 fix search issue in readthedocs

created custom search.html file and update in mkdocs.yml file
also updated yaml file with strict set to true. This fails the
documentation build if it detemines a broken link.

https://jira.hyperledger.org/browse/FAB-385

Change-Id: I6f7a60d980af07e14c8b2940d1aa224108c6416a
Signed-off-by: rameshthoomu <[email protected]>

Author: rameshthoomu

docs/custom_theme/searchbox.html

@@ -0,0 +1,5 @@
+<div role="search">
+  <form id ="rtd-search-form-alt" class="wy-form" action="{{ base_url }}/search.html" method="get">
+    <input type="text" name="q" placeholder="Search docs" />
+  </form>
+</div>

mkdocs.yml

@@ -3,6 +3,8 @@ site_url: http://hyperledger-fabric.readthedocs.io
 theme: readthedocs
 repo_url: http://gerrit.hyperledger.org/r/fabric
 site_description: 'Welcome to the Hyperledger fabric documentation'
+strict: true
+theme_dir: 'docs/custom_theme'
 
 pages:
 - Home: index.md