Fix illegal characters in README.md

[garzfaust]

Section: Object fields

This scenario of referencing ids could also be solved differently through a field of type �number�. It all depends on what you need.

Section: Form frame

The form has the FormFrame attached to it. It is a basic visual element which comes with a title and buttons. The reason for this is that you can use the �Form� as the root element so that you can use its �value� property directly. For convenience the Form yields the same properties as the FormFrame and the constructor even accepts its title.

Section: Widgets

�invisble�
�disabled�
�label�
�required�
error