include links from player and machine var index doc pages to config references

Author: bosh

docs/machine_vars/index.md

@@ -4,7 +4,6 @@ title: Machine Variables
 
 # Machine Variables
 
-
 MPF uses the concept of *machine variables* to track dynamically-created
 variables that apply on a machine-wide basis. Machine variables are
 similar in concept to
@@ -41,12 +40,17 @@ with your variable name. If you want to access the machine variable in a player,
 `{machine.my_var_name}`. In other words, when using the the first notation with the pipe symbol you access the value of the variable
 as a string, in the latter case using the dot notation you access the value itself.
 
-Video about player and machine variables:
+### Video about machine and [player variables](../player_vars/index.md):
 
 <div class="video-wrapper">
 <iframe width="560" height="315" src="https://www.youtube.com/embed/PUxEsNUGXPY" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
 </div>
 
+## Related Configs
+
+* [machine_vars: Config Reference](../config/machine_vars.md)
+* [variable_player: Config Reference](../config/variable_player.md)
+
 You can create your own machine variables in your configs. There are
 also several machine variables that are automatically created. Here's a
 list of the machine variables that are "built in" and available for

docs/player_vars/index.md

@@ -4,19 +4,23 @@ title: Player Variables Reference
 
 # Player Variables Reference
 
-
 Here's a list of all the different "built in"
 [player variables](../game_logic/players.md) that MPF uses.
 
 You can use these in your config files to trigger game logic or to
 display as text on your display.
 
-Video about player and machine variables:
+### Video about player and [machine variables](../machine_vars/index.md):
 
 <div class="video-wrapper">
 <iframe width="560" height="315" src="https://www.youtube.com/embed/PUxEsNUGXPY" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
 </div>
 
+## Related Configs
+
+* [player_vars: Config Reference](../config/player_vars.md)
+* [variable_player: Config Reference](../config/variable_player.md)
+
 Note that you can also create your own player variables in your configs,
 and most likely your machine will have several orders of magnitude more
 player variables than this list here.