Add width setting for the file finder (#18682)

This PR adds the ability to adjust the width of the file finder popup. I
found when searching my projects the default width was not always wide
enough and there was no option to change it.

It allows values `small`, `medium` (default), `large`, `xlarge`, and
`full`

Release Notes:

- Added a setting to adjust the width of the file finder modal


Example Setting:
```json
  "file_finder": {
    "modal_width": "medium"
  },
```

Screenshots can be found in the comments below.

docs/src/configuring-zed.md

@@ -1416,6 +1416,14 @@ Or to set a `socks5` proxy:
 
 `boolean` values
 
+## File Finder
+
+### Modal Width
+
+- Description: Width of the file finder modal. Can take one of a few values: `small`, `medium`, `large`, `xlarge`, and `full`.
+- Setting: `modal_width`
+- Default: `medium`
+
 ## Preferred Line Length
 
 - Description: The column at which to soft-wrap lines, for buffers where soft-wrap is enabled.