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>

docs/src/configuring-zed.md

@@ -2262,6 +2262,7 @@ Run the `theme selector: toggle` action in the command palette to see a current
     "button": true,
     "default_width": 240,
     "dock": "left",
+    "entry_spacing": "comfortable",
     "file_icons": true,
     "folder_icons": true,
     "git_status": true,
@@ -2303,6 +2304,30 @@ Run the `theme selector: toggle` action in the command palette to see a current
 }
 ```
 
+### Entry Spacing
+
+- Description: Spacing between worktree entries
+- Setting: `entry_spacing`
+- Default: `comfortable`
+
+**Options**
+
+1. Comfortable entry spacing
+
+```json
+{
+  "entry_spacing": "comfortable"
+}
+```
+
+2. Standard entry spacing
+
+```json
+{
+  "entry_spacing": "standard"
+}
+```
+
 ### Git Status
 
 - Description: Indicates newly created and updated files