Add support for weight, fill/stroke, and rounded/square

[jcfilben]

It would be nice if grommet icons supported the following:

1. setting a weight on the icon
2. having a boolean prop that controlled if the icon svg displays as fill or stroke
3. a boolean prop that controlled if the icon was rounded or square. See Home vs HomeRounded. Ideally instead of 2 icons for Home and HomeRounded there could be one icon and the round vs square could be controlled with a prop.