## setZIndex
### Description
Sets the z-index for the object. A higher value means a higher draw and event priority. You can also add multiple objects to the same z-index; in this case, the last added object will have the highest priority.
### Parameters
1. `number` z-index
### Returns
1. `object` The object in use
### Usage
* Sets the button's z-index to `1` and the label's z-index to `2`
```lua
local basalt = require("basalt")
local mainFrame = basalt.createFrame()
local aButton = mainFrame:addButton():setZIndex(1):setPosition(2,2)
local aLabel = mainFrame:addLabel():setZIndex(2):setPosition(2,2):setText("I am a label!")
```
```xml
```