description tag should be added in auto-completion

It will be good if we add a "description" tag as well in auto-completion option

i.e.  for example in case of leaf

```
leaf leaf-name {
            type type-name {
                
            }
}
```
to
```
leaf leaf-name {
            description "TODO: add description";
            type type-name {
                
            }
        }
```