Design and implement readonly version of missing form components

[GomezIvann]

This task involves both the design and implementation of the functionality since it is not just a technical feature. Add prop readOnly to the new form components:

• Add the readOnly prop to the Textarea component #1685
• Add the readOnly prop to the Text Input component #1687
• Add the readOnly prop to the Date Input component  #1689
• Add the readOnly prop to the Checkbox component #1692
• Add the readOnly prop to the Number Input component #1697
• Rename readonly prop to readOnly in Radio Group #1694

The read-only state has some key features:

• When it's true, it disables the onChange event. No interaction with the component changes its value.
• The regular states of the component work as usual (focus, hover, active, etc.).
• Changes the look of the component.
• It sends the value in the submit event.

[GomezIvann]

Requested also in #1290.