Update Crowdstrike Readme

[ellis-elastic]

Added link to Crowdstrike docs

Type of change

• Enhancement

What does this PR do?

Added link to Crowdstrike docs

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

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• Start Time: 2022-04-27T20:34:40.289+0000

• Duration: 14 min 35 sec

Test stats 🧪

Test	Results
Failed	0
Passed	13
Skipped	0
Total	13

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (2/2)	💚
Files	100.0% (9/9)	💚 2.857
Classes	100.0% (9/9)	💚 2.857
Methods	100.0% (52/52)	💚 11.905
Lines	91.327% (1432/1568)	👍 2.489
Conditionals	100.0% (0/0)	💚