Add Style Examples To Doc

[phidias51]

Please add more styling examples to the doc. Specifically examples that show how to set the height and width. iron-icon uses --iron-icon-height, and --iron-icon-width so the expectation is that --paper-icon-button-height and --paper-icon-width should do the trick here. Since that's not the case, some doc would help.

[hemantjadon]

I have added the required docs. Please Review

[notwaldorf]

This was already fixed