Adding documentation for markdown strings

packages/mermaid/src/docs/syntax/flowchart.md

@@ -446,6 +446,31 @@ flowchart LR
   B1 --> B2
 ```
 
+## Markdown Strings
+
+The "Markdown Strings" feature enhances flowcharts and mind maps by offering a more versatile string type, which supports text formatting options such as bold and italics, and automatically wraps text within labels.
+
+```mermaid-example
+%%{init: {"flowchart": {"htmlLabels": false}} }%%
+flowchart LR
+subgraph "One"
+  a("`The **cat**
+  in the hat`") -- "edge label" --> b{{"`The **dog** in the hog`"}}
+end
+subgraph "`**Two**`"
+  c("`The **cat**
+  in the hat`") -- "`Bold **edge label**`" --> d("The dog in the hog")
+end
+```
+
+Formatting:
+
+- For bold text, use double asterisks \*\* before and after the text.
+- For italics, use single asterisks \* before and after the text.
+- With traditional strings, you needed to add <br> tags for text to wrap in nodes. However, markdown strings automatically wrap text when it becomes too long and allows you to start a new line by simply using a newline character instead of a <br> tag.
+
+This feature is applicable to node labels, edge labels, and subgraph labels.
+
 ## Interaction
 
 It is possible to bind a click event to a node, the click can lead to either a javascript callback or to a link which will be opened in a new browser tab. **Note**: This functionality is disabled when using `securityLevel='strict'` and enabled when using `securityLevel='loose'`.