The mapping between vCard's XML elements and YAML elements
of 'vcard' option is straightforward. For example, if you
want mod_muc to return the following vCard:
```
<vCard xmlns='vcard-temp'>
<FN>Conferences</FN>
<ADR>
<WORK/>
<STREET>Elm Street</STREET>
</ADR>
</vCard>
```
you need to set the configuration as:
```
modules:
...
mod_muc:
vcard:
fn: Conferences
adr:
-
work: true
street: Elm Street
...
```
