Web Components page has outdated documentation vs README

[rhyeen]

Description

The documentation at paper-item web components documentation is not synced with the README.md.

For example, on the web component's site, it says, "The child node with the attribute item-icon is placed in the icon area." while the README says, "The child node with the slot item-icon is placed in the icon area."

Expected outcome

<iron-icon icon="favorite" item-icon></iron-icon> is stated to work on the web components site. It should have worked to apply item-icon as an attribute.

Actual outcome

It did not work, because the actual expectation is as follows: <iron-icon icon="favorite" slot="item-icon"></iron-icon>