Update UPGRADING.md

Author: brendt

UPGRADING.md

@@ -1,3 +1,7 @@
+## 2.8.0
+
+- Add Dockerfile support (#135)
+
 ## 2.7.0
 
 - Rename BOOLEAN token to LITERAL token (#128)
@@ -206,4 +210,4 @@ $highlighter = (new \Tempest\Highlight\Highlighter())->withGutter();
 }
 ```
 
-**Note**: This package doesn't account for `pre` tag styling. You might need to make adjustments to how you style `pre` tags if you enable gutter support.
+**Note**: This package doesn't account for `pre` tag styling. You might need to make adjustments to how you style `pre` tags if you enable gutter support.