[mwc-textfield] add name property to input

[fernandopasik]

Is your feature request related to a problem? Please describe.
Want a way to put a name property into the input element inside the textfield so a wrapping form can access it

Describe the solution you'd like
Have the name property and forward it to the input element

Describe alternatives you've considered
To use the textfield I've selected the mwc-textfield elements manually and extracted the value property

[fernandopasik]

Looking at this issue a bit more, I realize that since the input is in shadow dom, a wrapping form element won't be able to see this in the FormElement.elements property.

Is it in consideration to append the input through light dom? That would make the input element accessible from a wrapping form element.

[dfreedm]

Related #289

[fernandopasik]

I think this one can be closed as it's now in the new text-field component
https://github.com/material-components/material-web/blob/master/textfield/lib/text-field.ts#L140