Update docs about rendering templates

docs/templates.rst

@@ -55,6 +55,10 @@ standard go template functions, Kanister imports all the `sprig
     }
     return ras, nil
 
+Kanister will error during template rendering if FIPS non compliant
+sprig functions are used. The unsupported functions include: ``bcrypt``,
+``derivePassword``, ``htpasswd`` and ``genPrivateKey`` for key type ``dsa``.
+
 
 Objects
 =======