Add link to click/#373 issue to readme

Author: espdev

README.md

@@ -24,6 +24,7 @@ At the same time, many Click users need this functionality.
 You can read interesting discussions about it in the following issues:
 
 * [issue 257](https://github.com/pallets/click/issues/257)
+* [issue 373](https://github.com/pallets/click/issues/373)
 * [issue 509](https://github.com/pallets/click/issues/509)
 * [issue 1137](https://github.com/pallets/click/issues/1137)