docs: add example output file format for WRANGLER_OUTPUT_FILE environment variables

Add a comprehensive example showing the ND-JSON format of the output file,
including sample entries for wrangler-session and deploy operations, along
with descriptions of other entry types (version-upload, version-deploy,
pages-deploy, command-failed).

Co-Authored-By: pbacondarwin@cloudflare.com <pete@bacondarwin.com>

Author: devin-ai-integration[bot]

src/content/docs/workers/wrangler/system-environment-variables.mdx

@@ -95,6 +95,23 @@ Wrangler supports the following environment variables:
 
   - Specifies a directory where Wrangler will create a randomly-named file (format: `wrangler-output-<timestamp>-<random>.json`) to write output data in [ND-JSON](https://github.com/ndjson/ndjson-spec) format. This is useful when you want to keep output files organized in a specific directory but don't need to control the exact filename. If both `WRANGLER_OUTPUT_FILE_PATH` and `WRANGLER_OUTPUT_FILE_DIRECTORY` are set, `WRANGLER_OUTPUT_FILE_PATH` takes precedence.
 
+### Example output file
+
+When these environment variables are set, Wrangler writes one JSON object per line to the output file. Each entry includes a `timestamp` field and a `type` field indicating the kind of operation. Here's an example of what the file might contain after running `wrangler deploy`:
+
+```json
+{"type":"wrangler-session","version":1,"wrangler_version":"3.78.0","command_line_args":["deploy"],"log_file_path":"/path/to/logs/wrangler-2024-11-03_12-00-00_abc.log","timestamp":"2024-11-03T12:00:00.000Z"}
+{"type":"deploy","version":1,"worker_name":"my-worker","worker_tag":"abc123def456","version_id":"v1-abc123","targets":["https://my-worker.example.workers.dev"],"worker_name_overridden":false,"wrangler_environment":"production","timestamp":"2024-11-03T12:00:05.000Z"}
+```
+
+The `wrangler-session` entry is written when Wrangler starts and contains information about the command being run. The `deploy` entry is written when a deployment completes successfully and includes the worker name, version ID, and deployment URLs.
+
+Other entry types include:
+- `version-upload` - Written by `wrangler versions upload` with version ID and preview URLs
+- `version-deploy` - Written by `wrangler versions deploy` with deployment information
+- `pages-deploy` - Written by `wrangler pages deploy` with Pages deployment details
+- `command-failed` - Written when a command fails, including error code and message
+
 ## Example `.env` file
 
 The following is an example `.env` file: