doc: add changelog

Signed-off-by: Ali Caglayan <[email protected]>

Author: Alizter

doc/changes/11980.md

@@ -0,0 +1,4 @@
+- `dune runtest` can now run individual tests from a `(test (name foo))`
+  stanza as `dune runtest foo` and inline tests
+  `(library (name bar) (inline_tests))` as `dune runtest bar`
+  (#11980, grant #870, @Alizter).