_sass: Add inline-icon class

_sass/custom/custom.scss

@@ -93,6 +93,15 @@ summary {
   }
 }
 
+.inline-icon {
+  background-color: #f5f6fa;
+  border-radius: 4px;
+  height: 1.5em;
+  margin-bottom: -0.4em;
+  padding: 0.4em;
+  vertical-align: baseline;
+}
+
 [style*="--aspect-ratio"] > :first-child {
   width: 100%;
 }