internal/compiler: add .mdx as default Markdown file extension

This update sets Scriggo to recognize files with the '.mdx' extension as
Markdown by default. It ensures that files using this extension are
treated as Markdown files in the Scriggo environment.

internal/compiler/parser_template.go

@@ -326,7 +326,7 @@ func readFileAndFormat(fsys fs.FS, name string) ([]byte, ast.Format, error) {
 			format = ast.FormatJS
 		case ".json":
 			format = ast.FormatJSON
-		case ".md", ".mkd", ".mkdn", ".mdown", ".markdown":
+		case ".md", ".mdx", ".mkd", ".mkdn", ".mdown", ".markdown":
 			format = ast.FormatMarkdown
 		}
 	}

templates.go

@@ -84,7 +84,7 @@ var formatTypes = map[ast.Format]reflect.Type{
 //	CSS        : .css
 //	JavaScript : .js
 //	JSON       : .json
-//	Markdown   : .md .mkd .mkdn .mdown .markdown
+//	Markdown   : .md .mdx .mkd .mkdn .mdown .markdown
 //	Text       : all other extensions
 //
 // If the named file does not exist, BuildTemplate returns an error satisfying