ESLint one-var, no-var rules (#3239)

* fixed issues for eslint one-var and no-var rules

Co-authored-by: Joshi <simplyrender@gmail.com>
Co-authored-by: Andrew Henry <akhenry@gmail.com>

openmct.js

@@ -32,6 +32,6 @@ if (document.currentScript) {
 
 const MCT = require('./src/MCT');
 
-var openmct = new MCT();
+const openmct = new MCT();
 
 module.exports = openmct;