Update changelog for next release version (#857)

Author: Piszmog

CHANGELOG.md

@@ -13,14 +13,18 @@ All notable changes to `src-cli` are documented in this file.
 
 ### Added
 
-- Mounting files now works when running batch changes server side. [sourcegraph/src-cli#816](https://github.com/sourcegraph/src-cli/pull/816)
-
 ### Changed
 
 ### Fixed
 
 ### Removed
 
+## 4.0.1
+
+### Added
+
+- Mounting files now works when running batch changes server side. [sourcegraph/src-cli#816](https://github.com/sourcegraph/src-cli/pull/816)
+
 ## 4.0.0
 
 ### Fixed