add content to the typography extension page

docs/src/demos/Extensions/Typography/index.spec.js

@@ -0,0 +1,53 @@
+context('/api/extensions/typography', () => {
+  before(() => {
+    cy.visit('/api/extensions/typography')
+  })
+
+  beforeEach(() => {
+    cy.get('.ProseMirror').then(([{ editor }]) => {
+      editor.clearContent()
+    })
+  })
+
+  it('should make an em dash from two dashes', () => {
+    cy.get('.ProseMirror')
+      .type('-- emDash')
+      .find('p')
+      .should('contain', '— emDash')
+  })
+
+  it('should make an ellipsis from three dots', () => {
+    cy.get('.ProseMirror')
+      .type('... ellipsis')
+      .find('p')
+      .should('contain', '… ellipsis')
+  })
+
+  it('should make an correct open double quote', () => {
+    cy.get('.ProseMirror')
+      .type('"openDoubleQuote"')
+      .find('p')
+      .should('contain', '“openDoubleQuote')
+  })
+
+  it('should make an correct close double quote', () => {
+    cy.get('.ProseMirror')
+      .type('"closeDoubleQuote"')
+      .find('p')
+      .should('contain', 'closeDoubleQuote”')
+  })
+
+  it('should make an correct open single quote', () => {
+    cy.get('.ProseMirror')
+      .type("'openSingleQuote'")
+      .find('p')
+      .should('contain', '‘openSingleQuote’')
+  })
+
+  it('should make an correct close single quote', () => {
+    cy.get('.ProseMirror')
+      .type("'closeSingleQuote'")
+      .find('p')
+      .should('contain', 'closeSingleQuote’')
+  })
+})