specs: add cypress test for fallbackLanguages

Author: palkan

Diff for: cypress/fixtures/tpl/docs.index.html

@@ -28,7 +28,7 @@
       alias: {
         '.*?/awesome':
           'https://raw.githubusercontent.com/docsifyjs/awesome-docsify/master/README.md',
-        '.*?/changelog':
+        '/changelog':
           'https://raw.githubusercontent.com/docsifyjs/docsify/master/CHANGELOG.md',
         '/.*/_navbar.md': '/_navbar.md',
         '/zh-cn/(.*)':
@@ -40,6 +40,7 @@
         '/es/(.*)':
           'https://raw.githubusercontent.com/docsifyjs/docs-es/master/$1'
       },
+      fallbackLanguages: ['es'],
       auto2top: true,
       coverpage: true,
       executeScript: true,

Diff for: cypress/integration/routing/fallback.spec.js

@@ -0,0 +1,9 @@
+context('config.fallbackLanguages', () => {
+  it('fallbacks respecting aliases', () => {
+    cy.visit('http://localhost:3000/#/es/');
+
+    cy.get('.sidebar-nav').contains('Changelog').click();
+
+    cy.get('#main').should('contain', 'Bug Fixes');
+  })
+});