Add docs for addDuplicate and addGroup functions

docs/04-functions.md

@@ -5,3 +5,4 @@
 On this page you will find the methods you can use in the query builder.
 
 * [addAggregateWindow()](functions/addAggregateWindow.md)
+* [addDuplicate()](functions/addDuplicate.md)

docs/functions/addDuplicate.md

@@ -0,0 +1,46 @@
+# Flux Query Builder Docs
+
+## Functions » addDuplicate()
+
+### Parameters:
+
+<table>
+  <tbody>
+    <tr>
+      <th>Name</th>
+      <th>Data type</th>
+      <th>Description</th>
+    </tr>
+    <tr>
+      <td>column</td>
+      <td>string</td>
+      <td>Column to duplicate.</td>
+    </tr>
+    <tr>
+      <td>as</td>
+      <td>string</td>
+      <td>Name to assign to the duplicate column.</td>
+    </tr>
+
+  </tbody>
+</table>
+
+
+### Example
+
+```php
+->addDuplicate('tag', 'tag_dup')
+```
+
+This will result in the following Flux function part:
+
+```
+|> duplicate(
+    column: "tag",
+    as: "tag_dup",
+)
+```
+
+### Extra resources
+
+* [Flux documentation](https://docs.influxdata.com/flux/v0.x/stdlib/universe/duplicate/)

docs/functions/addGroup.md

@@ -0,0 +1,46 @@
+# Flux Query Builder Docs
+
+## Functions » addGroup()
+
+### Parameters:
+
+<table>
+  <tbody>
+    <tr>
+      <th>Name</th>
+      <th>Data type</th>
+      <th>Description</th>
+    </tr>
+    <tr>
+      <td>columns</td>
+      <td>array</td>
+      <td>List of columns to use in the grouping operation.</td>
+    </tr>
+    <tr>
+      <td>mode</td>
+      <td>string</td>
+      <td>Grouping mode. Default is 'by'.</td>
+    </tr>
+
+  </tbody>
+</table>
+
+
+### Example
+
+```php
+->addGroup(['foo', 'bar'], 'by')
+```
+
+This will result in the following Flux function part:
+
+```
+|> group(
+    columns: ["foo", "bar"],
+    mode: "by"
+)
+```
+
+### Extra resources
+
+* [Flux documentation](https://docs.influxdata.com/flux/v0.x/stdlib/universe/group/)