add the strike extension documentation

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

@@ -0,0 +1,5 @@
+context('/api/extensions/strike', () => {
+  beforeEach(() => {
+    cy.visit('/api/extensions/strike')
+  })
+})

docs/src/demos/Extensions/Strike/index.vue

@@ -0,0 +1,54 @@
+<template>
+  <div v-if="editor">
+    <button @click="editor.focus().strike()" :class="{ 'is-active': editor.isActive('strike') }">
+      strike
+    </button>
+
+    <editor-content :editor="editor" />
+  </div>
+</template>
+
+<script>
+import { Editor } from '@tiptap/core'
+import { EditorContent } from '@tiptap/vue'
+import Document from '@tiptap/extension-document'
+import Paragraph from '@tiptap/extension-paragraph'
+import Text from '@tiptap/extension-text'
+// import Strike from '@tiptap/extension-strike'
+
+export default {
+  components: {
+    EditorContent,
+  },
+
+  data() {
+    return {
+      editor: null,
+    }
+  },
+
+  mounted() {
+    this.editor = new Editor({
+      extensions: [
+        Document(),
+        Paragraph(),
+        Text(),
+        // Strike(),
+      ],
+      content: `
+          <p>This isn’t striked through.</s></p>
+          <p><s>But that’s striked through.</s></p>
+          <p><del>And this.</del></p>
+          <p><strike>This too.</strike></p>
+          <p style="text-decoration: line-through">This as well.</p>
+        `,
+    })
+
+    window.editor = this.editor
+  },
+
+  beforeDestroy() {
+    this.editor.destroy()
+  }
+}
+</script>