Improving SVG mocking for tests

src/__mocks__/svgMock.js

@@ -1 +1,5 @@
-module.exports = () => 'mock SVG';
+import React from 'react';
+
+const SvgMock = () => <svg></svg>;
+
+export default SvgMock;

src/components/Header/__snapshots__/test.js.snap

@@ -19,7 +19,7 @@ exports[`Header rendering 1`] = `
       <a
         href="https://github.com/javallone/regexper-static"
       >
-        <Component />
+        <SvgMock />
         <Trans>
           Source on GitHub
         </Trans>