Added support for Mermaid diagramming library and gave one simple example of using it

Author: tleonhardt

docs/features/scripting.md

@@ -79,26 +79,23 @@ If the cmd2 application follows the [unix_design_philosophy](https://en.wikipedi
 
 The following diagram illustrates the different boundaries to keep in mind.
 
-    +---------------------------------------------+
-    |                                             |
-    | Py scripts                                  |
-    |                                             |
-    | +-----------------------------------------+ |
-    | |  CMD2 Application                       | |
-    | |                                         | |
-    | | +-------------------------------------+ | |
-    | | |   Class Library                     | | |
-    | | | +------+ +------+ +------+ +------+ | | |
-    | | | |      | |      | |      | |      | | | |
-    | | | |  C   | |  C   | |  C   | |  C   | | | |
-    | | | |      | |      | |      | |      | | | |
-    | | | +------+ +------+ +------+ +------+ | | |
-    | | |                                     | | |
-    | | +-------------------------------------+ | |
-    | |                                         | |
-    | +-----------------------------------------+ |
-    |                                             |
-    +---------------------------------------------+
+```mermaid
+flowchart LR
+    subgraph Py scripts
+        direction TB
+        subgraph cmd2 Application
+            direction TB
+            subgraph Class Library
+                direction TB
+                class1
+                class2
+                class3
+                class4
+            end
+        end
+    end
+
+```
 
 !!! note
 

mkdocs.yml

@@ -121,6 +121,10 @@ markdown_extensions:
   - pymdownx.keys
   - pymdownx.smartsymbols
   - pymdownx.superfences:
+      custom_fences:
+          - name: mermaid
+            class: mermaid
+            format: !!python/name:pymdownx.superfences.fence_code_format
   - pymdownx.tabbed:
       alternate_style: true
 
@@ -210,7 +214,7 @@ nav:
   - Meta:
       - doc_conventions.md
 
-# Include extra CSS to make some style adjustments
+# Include extra CSS to make some style adjustments for ReadTheDocs
 extra_css:
   - stylesheets/readthedocs.css