Added a mixxin guide for vue (#32948)

* Added a mixxin guide for vue

* renamed folder to lower case

* fix: corrected typo and grammar

guide/english/vue/mixins/index.md

@@ -0,0 +1,101 @@
+---
+title: Mixins
+---
+
+## Mixins
+
+A constant problem is that we use some small functions in a lot of Vue components.  Instead of copying them into each of them, we can create mixins. Those can be included and will then be merged into the current component.
+
+### Examples
+
+Let's look at the following example:
+
+We see here that the mixin is merged into the context of the Vue Component, data of the mixin will be merged as well.
+```javascript
+var myMixin = {
+  methods: {
+    hello: function(name) {
+      return "Hello " + name;
+    }
+  }
+};
+
+new Vue({
+  mixins: [myMixin],
+  created: function() {
+    console.log(this.hello("John"));
+  }
+});
+
+// this will return print: Hello John
+```
+
+```javascript
+var myMixin = {
+  created: function() {
+    console.log("running mixin constructor");
+  }
+};
+
+Here we see that the constructor of the mixin is always executed before that of the component.
+new Vue({
+  mixins: [myMixin],
+  created: function() {
+    console.log("running component constructor");
+  }
+})
+// this will print:
+// running mixin constructor
+// running component constructor
+```
+
+Here we see that the Component will override the definitions in the mixin if there is a conflict.
+```javascript
+var myMixin = {
+  methods: {
+    foo: {
+      console.log('mixin foo');
+    },
+    bar: {
+      console.log('mixin bar');
+    }
+  }
+};
+
+var comp = new Vue({
+  mixins: [myMixin],
+  methods: {
+    bar: function() {
+      console.log('component bar');
+    }
+  }
+});
+
+comp.foo(); // prints "mixin foo"
+comp.bar(); // prints "component bar"
+```
+
+In this case we can use it to make a global readOnly Variable
+```javascript
+// use global mixins carefully
+Vue.mixin({
+  data: function() {
+    return {
+      get greeting() {
+        return "World";
+      }
+    }
+  }
+});
+
+Vue.component('page-greeting', {
+  props: ,
+  template: `
+    <div>
+      <h1>
+        Hello {{ greeting }}
+      </h1>
+    </div>
+  `
+});
+```