update Cyberasrkpas readme

[ellis-elastic]

added link to vendor documentation

What does this PR do?

added link to vendor documentation

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

Author's Checklist

• [ ]

How to test this PR locally

Related issues

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[elasticmachine]

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• Start Time: 2022-05-18T13:24:36.004+0000

• Duration: 18 min 30 sec

Test stats 🧪

Test	Results
Failed	0
Passed	87
Skipped	0
Total	87

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (1/1)	💚
Files	100.0% (1/1)	💚 3.589
Classes	100.0% (1/1)	💚 3.589
Methods	100.0% (17/17)	💚 11.711
Lines	92.441% (856/926)	👍 3.423
Conditionals	100.0% (0/0)	💚

[elasticmachine]

Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

[leehinman]

LGTM