"ValidationOnType" preference setting is not working.

[nayankankariya]

Steps to reproduce:
1: Launch Brackets.
2: Create new php file and save it.
3: Write basic code of php like :

<?php
fopen()

4: Open Debug > Open Preferences Files
5: Change "validateOnType": "True" in brackets.json.
6: start writing any thing (e.g: fope) and observe the Diagnostic Problem.

Result:
While typing any thing, it is not showing Diagnostic Problem.
It is showing Diagnostic Problems after saving the files.

Expected Result:
As we change "ValidationOnType" value to "True" so, it should show Diagnostic Problems while typing.

[nayankankariya]

Fix is checked in as part of PR #14685