feat(FormControl): Add support for html size attribute

[Exxenoz]

Description
The commit of this PR adds support for the size attribute of select and input elements. This is especially useful in case someone wants to create a select table with multiple visible options. (Check https://www.w3schools.com/tags/att_select_size.asp for details.)

Changes

• Added htmlSize prop to FormControl.js and linked it to the size attribute of the underlaying component.
• Created a new test case in FormControlSpec.js to check if the html size attribute is properly set.
• Updated forms doc and added an html size example to the "Select" section.

Related issue
#4499