Add module as a type of <script>

Recently, JavaScript module would be getting used because almost all
browsers support it, so `module` could also be added in
`VALID_JAVASCRIPT_TAG_TYPES` as a `type` of `<script>`.

lib/better_html/test_helper/safe_erb/allowed_script_type.rb

@@ -6,7 +6,7 @@ module BetterHtml
   module TestHelper
     module SafeErb
       class AllowedScriptType < Base
-        VALID_JAVASCRIPT_TAG_TYPES = ["application/ld+json", "text/javascript", "text/template", "text/html"]
+        VALID_JAVASCRIPT_TAG_TYPES = ["application/ld+json", "text/javascript", "text/template", "text/html", "module"]
 
         def validate
           script_tags.each do |tag, _|