Support class-static-block proposal (#9476)

* Support class-static-block proposal

* Update changelog

changelog_unreleased/javascript/pr-9408.md

@@ -1,4 +1,4 @@
-#### Update to `@babel/parser` 7.12 (#9408 by @sosukesuzuki)
+#### Update to `@babel/parser` 7.12 (#9408, #9476 by @sosukesuzuki)
 
 Updated the JavaScript parser to [`@babel/parser` 7.12](https://babeljs.io/blog/2020/10/15/7.12.0). This fixes several bugs and supports some new syntax.
 
@@ -20,3 +20,19 @@ Due to a [bug in `@babel/parser`](https://github.com/babel/babel/issues/12209),
 let happy = "happy";
 export { happy as "😃" };
 ```
+
+##### Support class static blocks
+
+```js
+class C {
+  static #x = 42;
+  static y;
+  static {
+    try {
+      this.y = doSomethingWith(this.#x);
+    } catch {
+      this.y = "unknown";
+    }
+  }
+}
+```