Doc: Migrate Smaller Vector Tables

Migrate
https://cwiki.apache.org/confluence/display/NUTTX/Smaller+Vector+Tables
to official wiki

Signed-off-by: Ludovic Vanasse <[email protected]>

Author: lvanasse

Documentation/guides/index.rst

@@ -53,4 +53,5 @@ Guides
   semihosting.rst
   renode.rst
   signal_events_interrupt_handlers.rst  
-  signaling_sem_priority_inheritance.rst
+  signaling_sem_priority_inheritance.rst
+  smaller_vector_tables.rst