fix(image-alt): Exclude svg[role="img"] elements (#683)

Author: Matty J

lib/rules/image-alt.json

@@ -1,6 +1,6 @@
 {
   "id": "image-alt",
-  "selector": "img, [role='img']",
+  "selector": "img, [role='img']:not(svg)",
   "tags": [
     "cat.text-alternatives",
     "wcag2a",

test/integration/rules/image-alt/image-alt.html

@@ -16,3 +16,4 @@
 <img src="img.jpg" id="pass8" aria-labelledby="ninjamonkeys">
 <div role="img" alt="blah" id="violation6"></div>
 <div role="img" aria-label="blah" id="pass9"></div>
+<svg role="img" id="ignore1"><title>SVG Title</title></svg>