Support for non-latin characters in heading anchor links (#492)

lib/core/__tests__/toSlug.tests.js

@@ -0,0 +1,14 @@
+const toSlug = require('../toSlug');
+
+[
+  ['Hello world! ', 'hello-world'],
+  ['React 16', 'react-16'],
+  ['Hello.   // (world?)! ', 'hello-world'],
+  ['Привет мир! ', 'привет-мир'],
+  ['Über Café.', 'uber-cafe'],
+  ['Someting long ...', 'someting-long-'],
+].forEach(([input, output]) => {
+  test(`toSlug('${input}') -> '${output}'`, () => {
+    expect(toSlug(input)).toBe(output);
+  });
+});