document co-run zookeeper and bookie on same machine (#3242)
document co-run zookeeper and bookie on same machine (#3242)

### Motivation

Issue: https://github.com/apache/pulsar/issues/3213

### Modifications

update the readme to highlight this part

### Result

After your change, what will change.
massakam/pulsar,yahoo/pulsar,yahoo/pulsar,merlimat/pulsar,nkurihar/pulsar,massakam/pulsar,yahoo/pulsar,nkurihar/pulsar,merlimat/pulsar,yahoo/pulsar,merlimat/pulsar,nkurihar/pulsar,nkurihar/pulsar,massakam/pulsar,massakam/pulsar,merlimat/pulsar,massakam/pulsar,nkurihar/pulsar,yahoo/pulsar,nkurihar/pulsar,merlimat/pulsar,massakam/pulsar,nkurihar/pulsar,nkurihar/pulsar,merlimat/pulsar,yahoo/pulsar,nkurihar/pulsar