Allow configuring spacing of project panel entries (#16255)

Release Notes:

- Added `project_panel.entry_spacing` setting to configure spacing
between entries in the project panel.

### Comfortable (default)
```json
  "project_panel": {
    "entry_spacing": "comfortable",
```
<img width="1582" alt="Screenshot 2024-08-14 at 5 50 41 PM"
src="https://github.com/user-attachments/assets/3411a82e-7517-4095-bf4a-bbf40000a7cb">

### Standard
```json
  "project_panel": {
    "entry_spacing": "standard",
```
<img width="1582" alt="Screenshot 2024-08-14 at 5 50 54 PM"
src="https://github.com/user-attachments/assets/2c13d799-c405-4301-8214-1cb3cc641c92">

---------

Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

assets/settings/default.json

@@ -372,6 +372,8 @@
     "default_width": 240,
     // Where to dock the project panel. Can be 'left' or 'right'.
     "dock": "left",
+    // Spacing between worktree entries in the project panel. Can be 'comfortable' or 'standard'.
+    "entry_spacing": "comfortable",
     // Whether to show file icons in the project panel.
     "file_icons": true,
     // Whether to show folder icons or chevrons for directories in the project panel.