ADD #143 to docs

docs-src/RxDocument.md

@@ -67,6 +67,23 @@ This removes the document from the collection.
 myDocument.remove();
 ```
 
+### update()
+Updates the document based on the [mongo-update-syntax](https://docs.mongodb.com/manual/reference/operator/update-field/), based on [modifyjs](https://github.com/lgandecki/modifyjs#implemented).
+
+```js
+myDocument.update({
+    $inc: {
+        age: 1 // increases age by 1
+    },
+    $set: {
+        fistName: 'foobar' // sets firstName to foobar
+    }
+});
+await myDocument.save();
+```
+
+
+
 ### Observe $
 Calling this will return an [rxjs-Observable](http://reactivex.io/rxjs/manual/overview.html#observable) which emits all change-Events belonging to this document.
 

docs-src/RxQuery.md

@@ -13,6 +13,19 @@ const query = myCollection.find().where('age').lt(18);
 const removedDocs = await query.remove();
 ```
 
+
+## update()
+Runs and [update](./RxDocument.md#update) on every RxDocument of the query-result.
+
+```js
+const query = myCollection.find().where('age').gt(18);
+await query.update({
+    $inc: {
+        age: 1 // increases age of every found document by 1
+    }
+});
+```
+
 ## NOTICE: RxQuery's are immutable
 
 Because RxDB is a reactive database, we can do heavy performance-optimisation on query-results which change over time. To be able to do this, RxQuery's have to be immutable.