Update conf.py with list of Rediraffe 301 redirects. (#6833)

Added first batch of redirects. Please check if this is OK? Will a syntax error / typo  in the redirects will cause issues beyond Rediraffe?

'user_guide/APIs.html': 'explanation/api/index.html#apis',
    'user_guide/Pipelines.html': 'how_to/pipeline/index.html',
    'user_guide/Templates.html': 'how_to/templates/index.html',
    '_static/images/sazure_deployment.png': '_static/images/azure_deployment.png',
    'user_guide/Server_Configuration.html': 'how_to/server/index.html',

doc/conf.py

@@ -97,6 +97,14 @@
 rediraffe_redirects = {
     # Removal of the developer testing page
     'developer_guide/testing': 'developer_guide/index',
+    'user_guide/APIs.html': 'explanation/api/index.html#apis',
+    'user_guide/Pipelines.html': 'how_to/pipeline/index.html',
+    'user_guide/Templates.html': 'how_to/templates/index.html',
+    '_static/images/sazure_deployment.png': '_static/images/azure_deployment.png',
+    'user_guide/Server_Configuration.html': 'how_to/server/index.html',
+
+# Todo
+# https://panel.holoviz.org/user_guide/Customization.html : what page to redirect this to?
 }
 
 nbsite_analytics = {