struct-tag rule false-positive on json inline tag

**Describe the bug**
[struct-tag](https://github.com/mgechev/revive/blob/master/RULES_DESCRIPTIONS.md#struct-tag) produces warning for json inline tag `struct-tag: unknown option 'inline' in JSON tag (revive)`

**To Reproduce**
Steps to reproduce the behavior:
1. add 
```golang
type Beta struct {
    Alpha `json:",inline"`
}
```
2. Run revive with struct-tag rule enabled
