Update readme

Signed-off-by: Jack Cherng <[email protected]>

Author: jfcherng

README.md

@@ -174,7 +174,7 @@ $result = $diff->render($renderer);
 
 ## Renderer: JSON
 
-<details><summary>Click to expand the result</summary>
+<details><summary>Click to expand</summary>
 
 ```javascript
 [
@@ -322,20 +322,23 @@ $result = $diff->render($renderer);
 # Upgrading
 
 
-## From v2 to v3
+<details><summary>From v2 to v3</summary>
 
 - `$diffOptions` removes: `charLevelDiff` and `separateBlock`.
 - `$templateOptions` adds: `detailLevel` (similar to `charLevelDiff`, read docs) and `separateBlock` (exact the same one in `$diffOptions`).
 - `Jfcherng\Diff\Diff`'s `$a` (`$old`), `$b` (`$new`) are required in `__construct()`. (You may pass two empty arrays if you do not want to do anything at that moment.)
 - The look of "skipped" block in HTML renderers (`SideBySide` and `Inline`) have been changed. (You may have to tweak your CSS.)
 
+</details>
 
-## From v3 to v4
+<details><summary>From v3 to v4</summary>
 
 - `Jfcherng\Diff\Utility\SequenceMatcher` becomes [a new package](https://packagist.org/packages/jfcherng/php-sequence-matcher) by the namespace of `Jfcherng\Diff\SequenceMatcher`.
 - Factories under `Jfcherng\Diff\Utility\` are moved to `Jfcherng\Diff\Factory\`. For example, `Jfcherng\Diff\Utility\RendererFactory` is now `Jfcherng\Diff\Factory\RendererFactory`.
 - Non-abstract classes are no longer inheritable as they are added with `final` keywords. (This allows me to do more internal changes without causing possible BC breaks.)
 
+</details>
+
 
 # Acknowledgment