Add isAppender functionality to MediaPlaceholder (#1327)

lukewalczak · web-flow · commit 57459f98684a · 2019-09-30T09:51:34.000+02:00
* set ref of gutenberg to PR-17195
diff --git a/gutenberg b/gutenberg
@@ -1 +1 @@
-Subproject commit fea63772b6e2f71e7422c999e436c44bd3914021
+Subproject commit aeaf0a824d188d183205d85d92ad66defd1c2d26
