Issue #2106459 by chx: Fixed core config has everything as string.

core/modules/action/config/action.settings.yml

core/modules/aggregator/config/aggregator.settings.yml

...ules/aggregator/config/views.view.aggregator_rss_feed.yml

...les/block/custom_block/config/custom_block.type.basic.yml

core/modules/book/config/node.type.book.yml

core/modules/contact/config/contact.category.feedback.yml

core/modules/contact/config/contact.category.personal.yml

core/modules/contact/config/contact.settings.yml

core/modules/field/config/field.settings.yml

core/modules/file/config/views.view.files.yml

core/modules/filter/config/filter.format.plain_text.yml

...g/field.instance.taxonomy_term.forums.forum_container.yml

core/modules/forum/config/forum.settings.yml

core/modules/forum/config/node.type.forum.yml

core/modules/image/config/image.style.large.yml

core/modules/image/config/image.style.medium.yml

core/modules/image/config/image.style.thumbnail.yml

core/modules/language/config/language.entity.en.yml

core/modules/language/config/language.entity.und.yml

core/modules/language/config/language.entity.zxx.yml