Update index.xml

Adding 2 more companies for training, this request came from @HowardTwine, these companies were added to the 3.13 docs on the 19.03 via PR: #1845

site/index.xml

@@ -234,8 +234,10 @@ limitations under the License.
               <p>The following companies provide free, virtual, or instructor-led courses for RabbitMQ:
                 <a href="https://mylearn.vmware.com/mgrReg/courses.cfm?ui=www_edu&amp;a=one&amp;id_subject=94112" target="_blank" rel="noopener noreferrer">VMware</a>,
                 <a href="https://www.erlang-solutions.com/products/rabbitmq.html">Erlang Solutions</a>,
-                <a href="http://www.visualintegrator.com/rmq/" target="_blank" rel="noopener noreferrer">Visual Integrator, Inc</a> and
-                <a href="https://www.learnquest.com/course-detail-v3.aspx?cnum=rabbitmq-e1xc" target="_blank" rel="noopener noreferrer">LearnQuest</a>.
+                <a href="http://www.visualintegrator.com/rmq/" target="_blank" rel="noopener noreferrer">Visual Integrator, Inc</a>, 
+                <a href="https://www.learnquest.com/course-detail-v3.aspx?cnum=rabbitmq-e1xc" target="_blank" rel="noopener noreferrer">LearnQuest</a>, 
+                <a href="https://seventhstate.io/" target="_blank" rel="noopener noreferrer">Seventh State</a>, and 
+                <a href="https://www.coders51.com/" target="_blank" rel="noopener noreferrer">Coders 51</a>,.
               </p>
             </div>
           </div>