Improve responsiveness of navbar in header and on challenge page (#4274)

Author: HarmvZ

app/grandchallenge/challenges/templates/challenges/challenge_topbar.html

@@ -3,8 +3,8 @@
 {% load guardian_tags %}
 
 {% if challenge %}
-    <nav class="navbar navbar-expand-lg navbar-light p-0 mb-3 mx-0 border-bottom align-items-start challenge-topbar">
-        <div class="col-auto mr-auto px-0">
+    <nav class="navbar navbar-expand-sm navbar-light p-0 mb-3 mx-0 border-bottom align-items-start challenge-topbar">
+        <div class="col mr-auto px-0">
             <ul class="nav navbar-nav nav-tabs">
                 <li class="nav-item">
                     <a class="nav-link {% if request.resolver_match.view_name == 'pages:home' or request.resolver_match.view_name == 'pages:detail' %} show active{% endif %}"

app/grandchallenge/core/templates/grandchallenge/partials/navbar.html

@@ -1,7 +1,7 @@
 {% load url %}
 {% load flatpages %}
 
-<nav class="navbar navbar-light navbar-top navbar-expand-lg sticky-top shadow bg-white">
+<nav class="navbar navbar-light navbar-top navbar-expand-md sticky-top shadow bg-white">
     <div class="container">
         <a class="navbar-brand mr-md-2 text-capitalize"
            href="{% url 'home' %}">