Clarify spec version

hail2u · hail2u · commit ef3efb91f47a · 2016-09-01T15:36:46.000+09:00
HTML 5.2 allows placing `figcaption` element anywhere inside of `figure`
element.
diff --git a/README.ja.md b/README.ja.md
@@ -834,7 +834,7 @@ Good:
 
 ### `figcaption`要素は`figure`要素の最初か最後に置く
 
-仕様では`figcaption`要素を`figure`要素の中ほどに置くことは許可されていません。
+仕様（WHATWG版）では`figcaption`要素を`figure`要素の中ほどに置くことは許可されていません。
 
 Bad:
 
diff --git a/README.md b/README.md
@@ -842,7 +842,8 @@ Good:
 
 ### Place `figcaption` element as first or last child of `figure` element
 
-Spec disallows `figcaption` element in the middle of `figure` element.
+Spec (WHATWG version) disallows `figcaption` element in the middle of `figure`
+element.
 
 Bad:
 
