added example of sort_by in the news. (#7196)

* added example of sort_by

* updated messgae

* tidy

---------

Co-authored-by: Michael Chirico <[email protected]>

Author: venom1204

NEWS.md

@@ -10,7 +10,16 @@
 
 ### NEW FEATURES
 
-1. New `sort_by()` method for data.tables, [#6662](https://github.com/Rdatatable/data.table/issues/6662). It uses `forder()` to improve upon the data.frame method and also match `DT[order(...)]` behavior with respect to locale. Thanks @rikivillalba for the suggestion and PR.
+1. New `sort_by()` method for data.tables, [#6662](https://github.com/Rdatatable/data.table/issues/6662). It uses `forder()` to improve upon the data.frame method and also matches `DT[order(...)]` behavior with respect to locale. Thanks @rikivillalba for the suggestion and PR.
+
+    ```r
+    DT = data.table(a=c(1L, 2L, 1L), b=c(3L, 1L, 2L))
+    sort_by(DT, ~a + b)
+    #    a b
+    # 1: 1 2
+    # 2: 1 3
+    # 3: 2 1
+    ```
 
 2. `melt()` now supports using `patterns()` with `id.vars`, [#6867](https://github.com/Rdatatable/data.table/issues/6867). Thanks to Toby Dylan Hocking for the suggestion and PR.