fix(yaml): preserve trailing whitespace in block scalars (#19764)

changelog_unreleased/yaml/19764.md

@@ -0,0 +1,14 @@
+#### Preserve trailing whitespace in YAML block scalars (#19764 by @splincode)
+
+Prettier now preserves trailing spaces, tabs, and whitespace-only lines when formatting literal and folded YAML block scalars.
+
+```js
+await prettier.format("foo: |-\n  value  \n", { parser: "yaml" });
+
+/* Prettier stable */
+// -> "foo: |-\n  value\n"
+
+/* Prettier main */
+// -> "foo: |-\n  value  \n"
+//                     ^^ spaces preserved
+```