Update changelog for #221

Author: axelson

CHANGELOG.md

@@ -6,6 +6,7 @@ Improvements:
 
 Bug Fixes:
 - Dialyzer: Get beam file for preloaded modules. (thanks [Łukasz Samson](https://github.com/lukaszsamson)) [#218](https://github.com/elixir-lsp/elixir-ls/pull/218)
+- Warn when using the debugger on Elixir 1.10.0-1.10.2. (thanks [Jason Axelson](https://github.com/axelson)) [#221](https://github.com/elixir-lsp/elixir-ls/pull/221)
 
 ### v0.3.3: 15 Apr 2020