StateNode atoms (#2213)

This PR extracts some improvements from #2198 into a separate PR.

### Release Notes
- adds computed `StateNode.getPath`
- adds computed StateNode.getCurrent`
- adds computed StateNode.getIsActive`
- adds computed `Editor.getPath()`
- makes transition's second property optional

### Change Type

- [x] `minor` — New feature

### Test Plan

- [x] Unit Tests
- [x] End to end tests

apps/examples/e2e/shared-e2e.ts

@@ -5,18 +5,6 @@ export function sleep(ms: number) {
 	return new Promise((resolve) => setTimeout(resolve, ms))
 }
 
-// export async function expectPathToBe(page: Page, path: string) {
-// 	expect(await page.evaluate(() => editor.root.path.value)).toBe(path)
-// }
-
-// export async function expectToHaveNShapes(page: Page, numberOfShapes: number) {
-// 	expect(await page.evaluate(() => editor.currentPageShapes.length)).toBe(numberOfShapes)
-// }
-
-// export async function expectToHaveNSelectedShapes(page: Page, numberOfSelectedShapes: number) {
-// 	expect(await page.evaluate(() => editor.selectedShapeIds.length)).toBe(numberOfSelectedShapes)
-// }
-
 declare const editor: Editor
 
 export async function setup({ page }: PlaywrightTestArgs & PlaywrightWorkerArgs) {