The parse fails when the value contains the end marker

### How to reproduce

separator: `###`
label_marker_start: `>>>`
label_marker_end: `<<<`

Issue body:
```md
### >>demo-repository-owner<<

octodemo

### >>template-type<<

repository

### >>template-owner<<

octodemo-resources

### >>template-repo<<

Markes: >> is start and is << end
```

---
### Proposed solution

Make the regex non greedy, see #8 