feat: add article for Vue.js Control Flow

Signed-off-by: João Daniel <jotaf.daniel@gmail.com>

client/src/pages/guide/english/vue/control-flow/index.md

@@ -0,0 +1,111 @@
+---
+title: Control Flow
+---
+
+## Control Flow
+
+
+### Conditionals
+
+With Vue.js you can decide wheter to show or not a piece of code in you final
+page, depending on some condition. For example, imagine a form input that is
+required a text at least 8 characters long: if the user input is shorter than 8,
+than an error message should appear; but if the input is longer than 8, the
+message disappears.
+
+But let's make a simpler example. We want to condition the exibition of a
+message to a counter:
+
+```html
+<div id="app">
+  <p v-if="counter > 10">
+    This message is only rendered when the counter is greater than 10
+  </p>
+</div>
+```
+
+```javascript
+let app = new Vue({
+  el: '#app',
+  data: {
+    counter: 0
+  }
+});
+```
+
+If you go to the console and start to increment the counter, when it crosses our
+threshold of 10, the message will be shown! Then, if you decrement `counter`,
+Vue.js will hide the message when `counter` gets lower than 10. For that, we
+used the directive `v-if`.
+
+And you might be wondering if there's an `else` for that `if`. And there is the
+`v-else`. Notice that the `v-else` will always
+* expect a `v-if` prior to it
+* refers to the closest `v-if` in the page
+
+Let's alter a little bit our first example to get this straight.
+
+```html
+<div id="app">
+  <p v-if="counter > 10">
+    This message is only rendered when the counter is greater than 10
+  </p>
+  <p v-else>
+    And this is the "otherwise" option
+  </p>
+</div>
+```
+
+```javascript
+let app = new Vue({
+  el: '#app',
+  data: {
+    counter: 0
+  }
+});
+```
+
+Play a little with that by changing `counter` values and pay attention to the
+message shown.
+
+Vue.js also has the `v-else-if` directive.
+
+
+### Loops
+
+Vue.js also helps with the generation of multiple copies of the same code
+structure, with loops. The classic example is a list dynamically rendered.
+
+```html
+<div id="app">
+  <ul>
+    <li v-for="item in list">
+      {{ item }}
+    </li>
+  </ul>
+</div>
+```
+
+```javascript
+let app = new Vue({
+  el: '#app',
+  data: {
+    list: [
+      "shave",
+      "do the dishes",
+      "clean the sink",
+      "pay the bill"
+    ]
+  }
+});
+```
+
+Way easier than inserting a lot of `<li>`. And notice that whenever the `list`
+changes, the result will change acordingly. Try it out: open the console and
+`push` some string to the `list` with
+
+```javascript
+app.list.push("something else");
+```
+
+As expected, the page rendered now has our brand new item!