Re includegraphics (#2053)

* Re-enable \includegraphics now that we have trust setting

This reverts commit 5806b240b3.

* Include Khan Academy test logo in repo and use in test (fix #1892)

* Update screenshots

* Update documentation

* Add tests, cleanup existing tests

* Update snapshots

* Enable trust testing (trust=true by default)

test/__snapshots__/katex-spec.js.snap

@@ -780,6 +780,62 @@ exports[`An implicit group parser within optional groups should work with sizing
 ]
 `;
 
+exports[`An includegraphics builder should not render without trust setting 1`] = `
+[
+  {
+    "attributes": {
+    },
+    "children": [
+      {
+        "classes": [
+          "mord",
+          "",
+          ""
+        ],
+        "depth": 0.25,
+        "height": 0.75,
+        "italic": 0,
+        "maxFontSize": 1,
+        "skew": 0,
+        "style": {
+          "color": "#cc0000"
+        },
+        "text": "\\\\includegraphics",
+        "width": 0.5
+      }
+    ],
+    "classes": [
+      "mord",
+      "text"
+    ],
+    "depth": 0.25,
+    "height": 0.75,
+    "maxFontSize": 1,
+    "style": {
+      "color": "#cc0000"
+    }
+  }
+]
+`;
+
+exports[`An includegraphics builder should render with trust setting 1`] = `
+[
+  {
+    "alt": "KA logo",
+    "classes": [
+      "mord"
+    ],
+    "depth": 0,
+    "height": 0.9,
+    "src": "https://cdn.kastatic.org/images/apple-touch-icon-57x57-precomposed.new.png",
+    "style": {
+      "height": "0.9em",
+      "width": "0.9em"
+    }
+  }
+]
+`;
+
 exports[`Extending katex by new fonts and symbols Add new font class to new extended symbols 1`] = `
 
 <span class="katex">