docs: added page about flavors

docs/flavors.md

@@ -0,0 +1,23 @@
+## Overview
+
+You can use _flavors_ (or presets) to set the preferred options automatically. In this way, Showdown behaves like popular Markdown flavors.
+
+Currently, the following flavors are available:
+
+ * `original`: Original Markdown flavor as in [John Gruber's spec](https://daringfireball.net/projects/markdown/)
+ * `vanilla`:  Showdown base flavor (v1.3.1 onwards)
+ * `github`: [GitHub Flavored Markdown, or GFM](https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax)
+
+## Set flavor
+
+=== "Globally"
+
+    ```js
+    showdown.setFlavor('github');
+    ```
+
+=== "Locally"
+
+    ```js
+    converter.setFlavor('github');
+    ```

mkdocs.yml

@@ -35,4 +35,5 @@ nav:
     - Compatibility: compatibility.md
   - Configuration:
     - Showdown options: configuration.md
-    - Available options: available-options.md
+    - Available options: available-options.md
+    - Flavors: flavors.md