Added Alt Tags to Imgs on HomePage (#6)

Author: nitin10s

_includes/menu.html

@@ -3,7 +3,7 @@
   <nav class="navbar navbar-expand-lg navbar-light bg-light" id="main-menu">
 
     <a class="navbar-brand" href="//bokeh.org" id="logo">
-      <img src="https://static.bokeh.org/logos/logotype.svg" height="30" width="110" />
+      <img src="https://static.bokeh.org/logos/logotype.svg" alt="Bokeh" height="30" width="110" />
     </a>
 
     <button class="navbar-toggler ml-auto hidden-sm-up float-xs-left" type="button" data-toggle="collapse" data-target="#navbarContent" aria-controls="navbarContent" aria-expanded="false" aria-label="Toggle navigation">

_includes/scenarios.html

@@ -54,7 +54,7 @@ <h2>Common Scenarios</h2>
       {% else %}
       <div class="tab-pane" id="tab-{{ item.short }}" role="tabpanel" aria-labelledby="{{ item.short }}-tab">
       {% endif %}
-        <img src="/img/{{ item.image }}" class="pb-2 scenarios-image" style="width: 400px; height: 280px" />
+        <img src="/img/{{ item.image }}" alt="{{ item.title }}" class="pb-2 scenarios-image" style="width: 400px; height: 280px" />
         <div class="container-fluid">
           <h4>{{ item.description }}</h4>
           {{ item.content }}

_includes/showcase.html

@@ -15,7 +15,7 @@ <h2>User Showcase</h2>
     {% assign items = site.users | sort: 'order' %}
     {% for item in items %}
     <div class="col-lg-3 col-md-6 col-sm-6">
-      <img src="/img/{{ item.image }}" />
+      <img src="/img/{{ item.image }}" alt="{{ item.name }}" />
     </div>
     <div class="col-lg-3 col-md-6 col-sm-6">
       <h4>{{ item.name }}</h4>