feat: add random port option to global http

[laojianzi]

Proposed Changes:

I don't want loggie to fail to start on hosts that use a large number of random ports due to fixed port assignments.

Additional documentation:

```yaml
http:
  enabled: true
  host: "0.0.0.0"
  port: 9196
  randPort: true
```

field	type	required	default	description
enabled	bool	false	false	whether to enable http
host	string	false	0.0.0.0	http listening host
port	int	false	9196	http listening port, If 'randPort' is enabled, this configuration will be ignored
randPort	bool	false	false	http listening random port