[Bug]: incomplete config documentation

[kordano]

What version of Datahike are you using?

0.4.0

What version of Java are you using?

openjdk version "11.0.11" 2021-04-20

What operating system are you using?

Ubuntu 20.04.3 LTS

What database EDN configuration are you using?

any

Describe the bug

The following configuration attributes are not documented:

• attribute-refs?
• index-config
• cache-size
• index

What is the expected behaviour?

The attributes should be documented in doc/config.md.

How can the behaviour be reproduced?

See config.md