PLANET-5773: CSL iframe not loading on posts

Ref: https://jira.greenpeace.org/browse/PLANET-5773

> it seems as though CSL iframes work fine on page but not on posts.

ControlShiftLabs iframe script relies on attributes
`id` and `data-petition-url` to insert its form.
We filter a post content before display in a certain way,
that is not applied to pages, and strips those attrributes..

Allowlisting those attributes allows CSL script to work.

src/MasterSite.php

@@ -595,7 +595,9 @@ public function set_custom_allowed_attributes_filter( $allowedposttags ) {
 		];
 
 		$allowedposttags['script'] = [
-			'src' => true,
+			'src'    => true,
+			'id'     => true,
+			'data-*' => true,
 		];
 
 		// Allow source tag for WordPress audio shortcode to function.