Fixed readonly and disabled field css style

[sahidhossen]

Pull Request for Issue #79 .

Summary of Changes

Change css style for read-only and disabled fields.

Testing Instructions

Expected result

Actual result

Documentation Changes Required

[joomlacorner]

Confirm patch worked.

[davidnguyen-joomlashine]

I confirmed the patch worked

[VanTrieuThanh]

I has checked but it still enable field

[sahidhossen]

@VanTrieuThanh Its should look like this.
Please check again in your local that you have received all changes.

[VanTrieuThanh]

@sahidhossen it has fine but field disable not same your attack. So user can misunderstanding