Update NEWS.md

Author: dmurdoch

NEWS.md

@@ -36,6 +36,7 @@
 * `unneeded_concatenation_linter` now correctly considers arguments piped in via magrittr `%>%` (#573, #585, @michaelquinn32)
 * Set the default `complexity_limit` in `cyclocomp_linter` to 15. This is the same complexity limit that is enforced via
   `default_linters` (#693, #695, @AshesITR).
+* `lint_package()` now lints files in the `demo` directory by default (#703, @dmurdoch).
 
 # lintr 2.0.1