style(CHANGELOG): Highlight code blocks in breaking changes

Author: ajoslin

CHANGELOG.md

@@ -59,28 +59,28 @@
 
   Before:
 
-    ```
-    <pagination first-text="<<" ...></pagination>
+    ```html
+    <pagination first-text="<<"></pagination>
     ```
 
   After:
 
-    ```
-    <pagination first-text="'<<'" ...></pagination>
+    ```html
+    <pagination first-text="'<<'"></pagination>
     ```
 
 - **progressbar:** 
  The 'value' is replaced by 'percent'.
 
   Before:
 
-    ```
+    ```html
     <progress value="..."></progress>
     ```
 
   After:
 
-    ```
+    ```html
     <progress percent="..."></progress>
     ```
 
@@ -92,7 +92,7 @@
 
   Before:
 
-    ```
+    ```html
     <tabs>
       <pane heading="one">
         First Content
@@ -105,7 +105,7 @@
 
   After:
 
-    ```
+    ```html
     <tabset>
       <tab heading="one">
         First Content