[fix] using different opensearch url to fix chrome POST request bug

searx/templates/opensearch.xml

   <Description>Search searx</Description>
   <InputEncoding>UTF-8</InputEncoding>
   <LongName>searx metasearch</LongName>
-  {% if method == 'get' %}
-    <Url type="text/html" method="get" template="{{ host }}?q={searchTerms}"/>
+  {% if opensearch_method == 'get' %}
+    <Url type="text/html" method="get" template="{{ host }}search?q={searchTerms}"/>
     {% if autocomplete %}
     <Url type="application/x-suggestions+json" method="get" template="{{ host }}autocompleter">
         <Param name="format" value="x-suggestions" />

searx/webapp.py

     return render_template(template_name, **kwargs)
 
 
+@app.route('/search', methods=['GET', 'POST'])
 @app.route('/', methods=['GET', 'POST'])
 def index():
     """Render index page.
         method = 'get'
 
     ret = render('opensearch.xml',
-                 method=method,
+                 opensearch_method=method,
                  host=get_base_url())
 
     resp = Response(response=ret,