Share menu improvements (#4079)

Improves share menu:
* Seems like we lost the logic of opening the share menu after sharing a
project.
* Using `/new` did open the share menu after creating a new room, but
the qr code flickered. This was because the create project action
created a new room but there were no search params set (for viewport and
page). So we first created the qr code for that url, but then we update
the url with those params and regenerate the qr code which caused the
flicker. That said the current logic does show a gray box a bit longer,
so not sure how much of an improvement this is.

### Before


https://github.com/tldraw/tldraw/assets/2523721/cdb4e3b8-46cb-48d9-bd23-66b2f4f55cff

### After


https://github.com/tldraw/tldraw/assets/2523721/f035bd48-6e59-4d3d-8e04-640c866c9395

### Change type

- [ ] `bugfix`
- [x] `improvement`
- [ ] `feature`
- [ ] `api`
- [ ] `other`

### Test plan

1. Share a local room. The share menu should be open after the redirect.

1. Use the `/new` route. The qr code in the share menu should not
flicker.

### Release notes

- Make sure the share menu is open after sharing a room. Prevent the qr
code from flickering when navigating to `/new`

apps/dotcom/src/components/ShareMenu.tsx

@@ -134,7 +134,12 @@ export const ShareMenu = React.memo(function ShareMenu() {
 		let cancelled = false
 
 		const shareUrl = window.location.href
-		if (!shareState.qrCodeDataUrl && shareState.state === SHARE_CURRENT_STATE.SHARED_READ_WRITE) {
+		const url = new URL(shareUrl)
+		if (
+			!shareState.qrCodeDataUrl &&
+			shareState.state === SHARE_CURRENT_STATE.SHARED_READ_WRITE &&
+			(url.searchParams.has('v') || url.searchParams.has('p'))
+		) {
 			// Fetch the QR code data URL
 			createQRCodeImageDataString(shareUrl).then((dataUrl) => {
 				if (!cancelled) {

apps/dotcom/src/utils/sharing.ts

@@ -165,7 +165,7 @@ export function useSharing(persistenceKey?: string): TLUiOverrides {
 							if (runningInIFrame) {
 								window.open(`${origin}${pathname}`)
 							} else {
-								navigate(pathname)
+								navigate(pathname, { state: { shouldOpenShareMenu: true } })
 							}
 						} catch (error) {
 							console.error(error)