Add docs for addReduce function

Signed-off-by: David Arendsen <darendsen@gamepoint.com>

docs/04-functions.md

@@ -5,7 +5,7 @@
 On this page you will find the methods you can use in the query builder.
 
 * [from()](functions/from.md)
-* [fromBucket()](functions/fromBucket.md)
+or [fromBucket()](functions/fromBucket.md)
 * [fromMeasurement()](functions/fromMeasurement.md)
 * [addAggregateWindow()](functions/addAggregateWindow.md)
 * [addDuplicate()](functions/addDuplicate.md)
@@ -13,5 +13,8 @@ On this page you will find the methods you can use in the query builder.
 * [addLimit()](functions/addLimit.md)
 * [addMean()](functions/addMean.md)
 * [addRangeStart()](functions/addRangeStart.md)
-* [addRangeInBetween()](functions/addRangeInBetween.md)
+or [addRangeInBetween()](functions/addRangeInBetween.md)
+* [addReduce()](functions/addReduce.md)
+
+Anything missing here? You can use this method to add anything to the query:
 * [addRawFunction()](functions/addRawFunction.md)

docs/functions/addReduce.md

@@ -0,0 +1,62 @@
+# Flux Query Builder Docs
+
+## Functions » addReduce()
+
+### Parameters:
+
+<table>
+  <tbody>
+    <tr>
+      <th>Name</th>
+      <th>Required</th>
+      <th>Data type</th>
+      <th>Description</th>
+    </tr>
+    <tr>
+      <td>settings</td>
+      <td>Yes</td>
+      <td>array</td>
+      <td>
+        Reducer calculation to apply to each row record.
+      </td>
+    </tr>
+    <tr>
+      <td>identity</td>
+      <td>Yes</td>
+      <td>array</td>
+      <td>Record that defines the reducer record and provides initial values for the reducer operation on the first row.</td>
+    </tr>
+  </tbody>
+</table>
+
+
+### Example
+
+```php
+use Arendsen\FluxQueryBuilder\Type\MathType;
+```
+
+```php
+->addReduce([
+  [
+    'count' => new MathType('accumulator.count + 1'),
+  ],
+  [
+    'count' => 0,
+  ]
+])
+```
+
+This will result in the following Flux function part:
+
+```
+|> reduce(fn: (r, accumulator) => ({
+    sum: r._value + accumulator.sum
+  }), 
+  identity: {sum: 0}
+)
+```
+
+### Extra resources
+
+* [Flux documentation](https://docs.influxdata.com/flux/v0.x/stdlib/universe/reduce/)