allow shell expansion when creating new file with names like `foo/+{layout,page}.svelte`

[BLucky-gh]

Check for existing issues

• [X] Completed

Describe the feature

currently, zed supports creating parent directories when creating files with / in the name, which is convenient, but I think it would also be convenient if the kind of expansion done by shells (as in {foo,bar}.baz -> foo.baz and bar.baz). A good example is making a new route in svelte and making both the page and the layout file at once

If applicable, add mockups / screenshots to help present your vision of the feature

No response