Blog post, changelog and docs for 1.19 (#6787)

.github/PULL_REQUEST_TEMPLATE.md

@@ -5,7 +5,7 @@
 
 - [ ] I’ve added tests to confirm my change works.
 - [ ] (If changing the API or CLI) I’ve documented the changes I’ve made (in the `docs/` directory)
-- [ ] (If the change is user-facing) I’ve added my changes to the `CHANGELOG.unreleased.md` file following the template.
+- [ ] (If the change is user-facing) I’ve added my changes to `changelog_unreleased/*/pr-XXXX.md` file following `changelog_unreleased/TEMPLATE.md`.
 - [ ] I’ve read the [contributing guidelines](https://github.com/prettier/prettier/blob/master/CONTRIBUTING.md).
 
 **✨[Try the playground for this PR](https://prettier.io/playground-redirect)✨**