feat: move uid to props (#1362)

* Add uniqueKey prop

* move uid to prop

* Update props.md

Co-authored-by: TheJaredWilcurt <4629794+TheJaredWilcurt@users.noreply.github.com>
Co-authored-by: Jeff Sagal <sagalbot@gmail.com>

docs/api/props.md

@@ -569,6 +569,18 @@ transition: {
 },
 ```
 
+## uid
+
+A unique identifier used to generate IDs and DOM attributes.
+Must be unique for every instance of the component.
+
+```js
+uid: {
+  type: [String, Number],
+  default: () => uniqueId(),
+},
+```
+
 
 ## value