Add notes on security

Author: wooorm

readme.md

@@ -47,6 +47,11 @@ embedded({
 
 Check if `node` is an [*embedded*][spec] [*element*][element].
 
+## Security
+
+`hast-util-embedded` does not change the syntax tree so there are no openings
+for [cross-site scripting (XSS)][xss] attacks.
+
 ## Contribute
 
 See [`contributing.md` in `syntax-tree/.github`][contributing] for ways to get
@@ -106,3 +111,5 @@ abide by its terms.
 [hast]: https://github.com/syntax-tree/hast
 
 [element]: https://github.com/syntax-tree/hast#element
+
+[xss]: https://en.wikipedia.org/wiki/Cross-site_scripting