Created a pull request to add an ‘is_single’ filter (https://github.com/Automattic/Ad-Code-Manager/pull/68)

Merged by @rinatkhaziev in https://github.com/Automattic/Ad-Code-Manager/commit/c4b80c129bb5b6ebe3efcf0b9545d7ef1becb6b8 and pushed to WordPress.com by myself in r71715.