docs(number-input): add empty value example

docs/src/pages/components/NumberInput.svx

@@ -19,6 +19,14 @@ components: ["NumberInput", "NumberInputSkeleton"]
 
 <NumberInput min="{4}" max="{20}" value="{4}" invalidText="Number must be between 4 and 20." helperText="Clusters provisioned in your region" label="Clusters (4 min, 20 max)" />
 
+### No value
+
+Set `allowEmpty` to `true` to allow for no value.
+
+Set `value` to `null` to denote "no value."
+
+<FileSource src="/framed/NumberInput/NumberInputEmpty" />
+
 ### Hidden label
 
 <NumberInput hideLabel label="Clusters" />

docs/src/pages/framed/NumberInput/NumberInputEmpty.svelte

@@ -0,0 +1,15 @@
+<script>
+  import { NumberInput, Button } from "carbon-components-svelte";
+
+  let value = null;
+</script>
+
+<NumberInput allowEmpty bind:value />
+
+<div style="margin: var(--cds-layout-01) 0">
+  <Button on:click="{() => (value = null)}">Set to null</Button>
+  <Button on:click="{() => (value = 0)}">Set to 0</Button>
+</div>
+
+<strong>Value:</strong>
+{value}