Update Rails HTML Sanitizer for wasm build

Author: rossta

lib/rails-wasm/rails-wasm-shim/stubs/rails-html-sanitizer.rb

@@ -1,4 +1,16 @@
 module Rails
+  module HTML
+    class Sanitizer
+      def sanitize(html, ...) = html
+
+      def sanitize_css(style) = style
+
+      def self.full_sanitizer = self
+
+      def self.best_supported_vendor = Rails::HTML4::Sanitizer
+    end
+  end
+
   module HTML4
     class Sanitizer
       def sanitize(html, ...) = html