img with alt maps to image

according to https://www.w3.org/TR/html-aria/ and https://www.w3.org/TR/html-aam-1.0/,
only images with `alt` explicitly set will map to `img` role.

lib/rules/role-supports-aria-props.js

@@ -44,15 +44,16 @@ module.exports = {
  // - Get the element’s name
  const key = {name: getElementType(context, node)}
  // - Get the element’s disambiguating attributes
- for (const prop of ['aria-expanded', 'type', 'size', 'role', 'href', 'multiple', 'scope']) {
+ for (const prop of ['alt', 'aria-expanded', 'type', 'size', 'role', 'href', 'multiple', 'scope']) {
  // - Only provide `aria-expanded` when it’s required for disambiguation
  if (prop === 'aria-expanded' && key.name !== 'summary') continue
+ if (prop === 'alt' && key.name !== 'img') continue
  const value = getPropValue(getProp(node.attributes, prop))
  if (value) {
  if (!('attributes' in key)) {
  key.attributes = []
  }
- if (prop === 'href') {
+ if (prop === 'href' || prop === 'alt') {
  key.attributes.push({name: prop})
  } else {
  key.attributes.push({name: prop, value})