Documentation: Add NML road stops random_bits_tile variable

docs/newgrf-roadstops-nml.html

@@ -131,7 +131,8 @@
 		<tr><td>company_colour2</td><td>COLOUR_XXX</td><td></td></tr>
 		<tr><td>animation_frame</td><td>0..255</td><td>Animation frame of the current tile</td></tr>
 		<tr><td>waiting_triggers</td><td>0..255</td><td>Waiting triggers</td></tr>
-		<tr><td>random_bits</td><td>0..16777215</td><td>Random bits</td></tr>
+		<tr><td>random_bits</td><td>0..16777215</td><td>All random bits</td></tr>
+		<tr><td>random_bits_tile</td><td>0..255</td><td>Random bits (per tile), see also <a href="https://newgrf-specs.tt-wiki.net/wiki/NML:Stations#Base_station_variables">random_bits_station</a></td></tr>
 		<tr><td>one_way_info</td><td>RST_OWI_XXX</td><td>One-way road information of drive-through stop tile<br />XXX = TWO_WAY | WEST_BOUND | EAST_BOUND | NO_ENTRY</td></tr>
 	</table>
 	<br />