ENYO-2950: allow to have  a file name with capital file extension into package.js

* Problem
When user change file extension letter case to Capital case letters, package.js doesn't have file info.

* Test Case (previous)
1) `/source/App.js` =(change)=> `/source/App.JS`
2) `/source/package.js` doesn't contains `App.JS`

* Test Case (expected result)
1) `/source/App.js` =(change)=> `/source/App.JS`
2) `/source/package.js` contains `App.JS`

Enyo-DCO-1.1-Signed-off-by: Junil Kim <logyourself@gmail.com>