docs: Update zookeeper-operator helm configuration docs

[cbuto]

Change log description

Update zookeeper-operator Helm configuration documentation.

Purpose of the change

Fixes #421

What the code does

Updates the charts/zookeeper-operator/README.md to reflect all the Helm configuration parameters for the zookeeper-operator chart.

How to verify it

(Steps to verify that the changes are effective)

[codecov]

Codecov Report

Merging #423 (e1efa7c) into master (75d75e7) will not change coverage.
The diff coverage is n/a.

❗ Current head e1efa7c differs from pull request most recent head 97e478b. Consider uploading reports for the commit 97e478b to get more accurate results

@@           Coverage Diff           @@
##           master     #423   +/-   ##
=======================================
  Coverage   84.11%   84.11%           
=======================================
  Files          12       12           
  Lines        1643     1643           
=======================================
  Hits         1382     1382           
  Misses        177      177           
  Partials       84       84           

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[anishakj]

@cbuto Thank you for the contribution

[anishakj]

LGTM