Link layers to styles if style already exist
Scenario:

Style already exists in shared styles.

I select a layer with the same name as the already available style.

Result: nothing happens
Expected result: I would expect that the layer would be linked to the shared style. 

My proposal for udpate:

```javascript
// update shared styles, and sync instances
const update = (sharedStyles, sharedStyle, layer) => {
  if (layer.hasOwnProperty('sharedStyle')) {
    layer.sharedStyle.style = layer.style;
  }else{
    layer.sharedStyleId = sharedStyle.id;
  }
```