Adding missing description for method and fixing typo

(cherry picked from commit 77b6f3e8129877d8a980f8cfdd95b8ef2ef978f6)

doc/classes/Particles.xml

@@ -15,13 +15,14 @@
 			<return type="AABB">
 			</return>
 			<description>
+				Returns the bounding box that contains all the particles that are active in the current frame.
 			</description>
 		</method>
 		<method name="restart">
 			<return type="void">
 			</return>
 			<description>
-				Restarts the particle emmission, clearing existing particles.
+				Restarts the particle emission, clearing existing particles.
 			</description>
 		</method>
 	</methods>