Add Custom Header component visualization

[yduartep]

The objective of this change is to have the possibility of display custom component, not just in the body of the modal, but also in the header.

• Added a new parameter in IModalDialogOptions named headerComponent used to store the custom Header component to be displayed.
• Added a new parameter in IModalDialogSettings named headerType that will have the default value TITLE or can be changed with the value CUSTOM. If the second value is defined, the headerComponent parameter becomes mandatory.
• New Unit test was added to test this new modal dialog behavior.
• A new button with the title "Dialog with custom header component" was added in the demo project to display the new case.