[Editor] Update the loading icon when wait for ML to take into accoun…

…t prefered-reduced-motion setting

 * The icon has been updated in https://bugzilla.mozilla.org/show_bug.cgi?id=1908920;
 * Add a linter to check that a svg element doesn't have fill="context-fill" attribute.

.svglintrc.js

@@ -0,0 +1,21 @@
+export default {
+  rules: {
+    valid: true,
+
+    custom: [
+      (reporter, $, ast, { filename }) => {
+        reporter.name = "no-svg-fill-context-fill";
+
+        const svg = $.find("svg");
+        const fill = svg.attr("fill");
+        if (fill === "context-fill") {
+          reporter.error(
+            "Fill attribute on svg element must not be set to 'context-fill'",
+            svg[0],
+            ast
+          );
+        }
+      },
+    ],
+  },
+};

gulpfile.mjs

@@ -1897,7 +1897,7 @@ gulp.task(
 
 gulp.task("lint", function (done) {
   console.log();
-  console.log("### Linting JS/CSS/JSON files");
+  console.log("### Linting JS/CSS/JSON/SVG files");
 
   // Ensure that we lint the Firefox specific *.jsm files too.
   const esLintOptions = [
@@ -1930,6 +1930,12 @@ gulp.task("lint", function (done) {
     prettierOptions.push("--log-level", "warn", "--check");
   }
 
+  const svgLintOptions = [
+    "node_modules/svglint/bin/cli.js",
+    "**/*.svg",
+    "--ci",
+  ];
+
   const esLintProcess = startNode(esLintOptions, { stdio: "inherit" });
   esLintProcess.on("close", function (esLintCode) {
     if (esLintCode !== 0) {
@@ -1950,8 +1956,24 @@ gulp.task("lint", function (done) {
           done(new Error("Prettier failed."));
           return;
         }
-        console.log("files checked, no errors found");
-        done();
+
+        const svgLintProcess = startNode(svgLintOptions, {
+          stdio: "pipe",
+        });
+        svgLintProcess.stdout.setEncoding("utf8");
+        svgLintProcess.stdout.on("data", m => {
+          m = m.toString().replace(/-+ Summary -+.*/ms, "");
+          console.log(m);
+        });
+        svgLintProcess.on("close", function (svgLintCode) {
+          if (svgLintCode !== 0) {
+            done(new Error("svglint failed."));
+            return;
+          }
+
+          console.log("files checked, no errors found");
+          done();
+        });
       });
     });
   });