created add-author template

bellapanghulan_reading/bookshelf/templates/bookshelf/add-author.html

+{%extends 'base.html'%}
+{% block title %} Add New Author {% endblock %}
+
+{% block body %}
+{% block content %}
+<form method="POST" action="">
+    {% csrf_token %}
+    {{form}}
+    <input type="Submit" value="Add Author">
+</form>
+{% endblock %}
+{% endblock %}
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