Update cisco_ios readme.md

[cherryleaf]

Added link to Cisco's documentation

Type of change

• Enhancement

What does this PR do?

Added link to Cisco's 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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• Start Time: 2022-07-19T22:34:39.446+0000

• Duration: 18 min 3 sec

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Test	Results
Failed	0
Passed	11
Skipped	0
Total	11

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (1/1)	💚
Files	100.0% (1/1)	💚 3.036
Classes	100.0% (1/1)	💚 3.036
Methods	100.0% (14/14)	💚 10.895
Lines	90.672% (243/268)	👍 0.312
Conditionals	100.0% (0/0)	💚