Added support for EXIT op (#397)

* EXIT op

* changelog

* docs

* Update CHANGELOG.md

CHANGELOG.md

@@ -6,6 +6,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 ### Added
+- Added support for `EXIT` opcode via `exit : (string) => 'a` function (behaves same as `ABORT`, but consumes all gas).
 - Compiler warnings for the follwing: shadowing, negative spends, division by zero, unused functions, unused includes, unused stateful annotations, unused variables, unused parameters, unused user-defined type, dead return value.
 - The pipe operator |>
   ```