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.

Author: khiga8

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})