Enabled travis build under node.js@15

.travis.yml

@@ -11,6 +11,8 @@ jobs:
       node_js: "12"
     - os: linux
       node_js: "13"
+    - os: linux
+      node_js: "14"
     - os: linux
       node_js: "stable"
     - os: windows

CHANGELOG.md

@@ -3,6 +3,7 @@ Change Log
 v2.6.2
 ---
 * Fixed installation in `PowerShell`. Fixed https://github.com/javascript-obfuscator/javascript-obfuscator/issues/783
+* Tested under `Node.js@15`
 
 v2.6.1
 ---