Illegal composer name

>   "name": "grav-plugin-markdown-notices",

Throws with composer@v2.8.6:

```
  "./composer.json" does not match the expected JSON schema:                                                  
   - name : Does not match the regex pattern ^[a-z0-9]([_.-]?[a-z0-9]+)*/[a-z0-9](([_.]|-{1,2})?[a-z0-9]+)*$  
```