Fixed broken link issues in roller ball tutorial doc. (#6024)

Author: miguelalonsojr

docs/Learning-Environment-Create-New.md

@@ -43,11 +43,7 @@ importing the ML-Agents assets into it:
 
 Your Unity **Project** window should contain the following assets:
 
-<p align="left">
-  <img src="images/roller-ball-projects.png"
-       alt="Project window"
-       width="250" border="10" />
-</p>
+![Unity Project Window](images/roller-ball-projects.png){: style="width:250px"}
 
 ## Create the Environment
 
@@ -64,11 +60,7 @@ to seek, and a Sphere to represent the Agent itself.
 1. Set Transform to Position = `(0, 0, 0)`, Rotation = `(0, 0, 0)`, Scale =
    `(1, 1, 1)`.
 
-<p align="left">
-  <img src="images/roller-ball-floor.png"
-       alt="The Floor in the Inspector window"
-       width="400" border="10" />
-</p>
+![Floor Inspector window](images/roller-ball-floor.png){: style="width:400px"}
 
 ### Add the Target Cube
 
@@ -78,11 +70,7 @@ to seek, and a Sphere to represent the Agent itself.
 1. Set Transform to Position = `(3, 0.5, 3)`, Rotation = `(0, 0, 0)`, Scale =
    `(1, 1, 1)`.
 
-<p align="left">
-  <img src="images/roller-ball-target.png"
-       alt="The Target Cube in the Inspector window"
-       width="400" border="10" />
-</p>
+![Target Cube Inspector window](images/roller-ball-target.png){: style="width:400px"}
 
 ### Add the Agent Sphere
 
@@ -108,11 +96,7 @@ To do so:
 1. Drag the Floor, Target, and RollerAgent GameObjects in the Hierarchy into the
    TrainingArea GameObject.
 
-<p align="left">
-  <img src="images/roller-ball-hierarchy.png"
-       alt="The Hierarchy window"
-       width="250" border="10" />
-</p>
+![Hierarchy window](images/roller-ball-hierarchy.png){: style="width:250px"}
 
 ## Implement an Agent
 
@@ -360,11 +344,8 @@ with our Agent script.
    - `Actions` > `Continuous Actions` = 2
 
 In the inspector, the `RollerAgent` should look like this now:
-<p align="left">
-  <img src="images/roller-ball-agent.png"
-       alt="The Agent GameObject in the Inspector window"
-       width="400" border="5" />
-</p>
+
+![Agent GameObject Inspector window](images/roller-ball-agent.png){: style="width:400px"}
 
 Now you are ready to test the environment before training.
 

mkdocs.yml

@@ -43,7 +43,7 @@ theme:
     # Palette toggle for light mode
     - scheme: default
       toggle:
-        icon: material/brightness-7 
+        icon: material/brightness-7
         name: Switch to dark mode
     # Palette toggle for dark mode
     - scheme: slate
@@ -56,3 +56,4 @@ extra_css:
 markdown_extensions:
     - markdown_include.include:
         base_path: docs
+    - attr_list