Added margin definitions to Premium Content Block

Added a generic .entry-content-child class to be used (extended) by
anything that needs to apply the content child margins.

Leveraged this .entry-content-child from a new Premium Content selector in
order for the appropraite vertical margins to be applied to premium
content.

varia/sass/blocks/_imports.scss

@@ -24,6 +24,7 @@
 @import "media-text/style";
 @import "paragraph/style";
 @import "posts-list/style";
+@import "premium-content/style";
 @import "pullquote/style";
 @import "quote/style";
 @import "separator/style";

varia/sass/blocks/premium-content/_style.scss

@@ -0,0 +1,10 @@
+.wp-block-premium-content-container {
+
+	.wp-premium-content-logged-out-view,
+	.wp-block-premium-content-subscriber-view {
+		> * {
+			@extend .entry-content-child;
+		}
+	}
+
+}

varia/sass/layout/_structure.scss

@@ -87,7 +87,7 @@
 .site-main > article > *, // apply vertical margins to article level
 .site-main > .not-found > *, // apply vertical margins to article level
 .entry-content > *,
-.entry-content p, // ensure all paragraphs, including nested ones, carry a margin
+.entry-content-child,
 [class*="inner-container"] > *,
 .widget-area > * {