use existing ID if assigned

closes #101

Author: CaptainCodeman

package.json

@@ -1,7 +1,7 @@
 {
 	"name": "svelte-headlessui",
 	"description": "HeadlessUI components for Svelte",
-	"version": "0.0.45",
+	"version": "0.0.46",
 	"type": "module",
 	"keywords": [
 		"svelte",
@@ -49,7 +49,7 @@
 	"homepage": "https://captaincodeman.github.io/svelte-headlessui/",
 	"repository": {
 		"type": "git",
-		"url": "https://github.com/captaincodeman/svelte-headlessui.git"
+		"url": "git+https://github.com/captaincodeman/svelte-headlessui.git"
 	},
 	"author": {
 		"name": "Simon Green",

src/lib/internal/new-id.ts

@@ -5,5 +5,5 @@ export function newID() {
 }
 
 export function ensureID(node: HTMLElement, prefix: string) {
-	node.id = `${prefix}:${newID()}`
+	node.id = node.id ||`${prefix}:${newID()}`
 }