Handlebars: Stop formatting <style lang=""> as CSS (#20031)

Co-authored-by: fisker <lionkay@gmail.com>

changelog_unreleased/handlebars/20031.md

@@ -0,0 +1,23 @@
+#### Don't format `<style lang="">` as CSS (#20031 by @kovsu)
+
+<!-- prettier-ignore -->
+```hbs
+{{! Input }}
+<style lang="">
+  .a { color: red;
+  }
+</style>
+
+{{! Prettier stable }}
+<style lang="">
+  .a {
+    color: red;
+  }
+</style>
+
+{{! Prettier main }}
+<style lang="">
+  .a { color: red;
+  }
+</style>
+```