[Feature]: Offer Option to Improve Default Filename of Exported SVG, PNG, etc.
### What's the feature?

At the moment, exporting a project as .svg, .png, .etc. leads the user to a save-file-as dialogue window that offers to save the exported file as `untitled.svg`. 

I'd like to propose the community consider two options to improve this default behavior. 

(I am currently using tldraw in VS Code via tldraw VS Code extension.)

##  Option 1: Default to current date & time

Example default filename: `20241027-1841.svg`.

I use tldraw to embed .svg/.png illustrations as figures and math handwriting in documents (e.g., Markdown, Typst). Each time I export a tldraw project to a .svg/.png file, I have to think of a filename that (i) hasn't been used, and (ii) somewhat makes sense. 

Excalidraw's Obsidian plugin (Obsidian is a markdown app) has an option to save drawings with a filename that's the current date & time. The following screenshot illustrates how this might look like:

![Screenshot 2024-10-27 at 3 30 03 AM](https://github.com/user-attachments/assets/3bae0c81-ea3b-453b-a415-bf901164821d)

tldraw's Obsidian plugin does the same, but tldraw's VS Code extension does not seem to have this 😢

![Screenshot 2024-10-27 at 3 32 20 AM](https://github.com/user-attachments/assets/6ba98601-26bf-4539-b8fd-8b30109e76f8)

##  Option 2: Default to .tldr project name

This one is reasonable in the sense that it associates the exported .svg/.png to the tldraw project by filename.

### Where would you like this feature?

The developer package

### Contact Details

_No response_

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct