[Cloudflare]: update documentation

[r00tu53r]

What does this PR do?

Update Cloudflare 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.

How to test this PR locally

Pipeline Tests
elastic-package test pipeline

System Tests
elastic-package test system

Related issues

• Closes Cloudflare documentation needs more details #3227

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

[elasticmachine]

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Build stats

• Start Time: 2022-04-29T09:04:36.170+0000

• Duration: 15 min 21 sec

Test stats 🧪

Test	Results
Failed	0
Passed	96
Skipped	0
Total	96

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (2/2)	💚
Files	100.0% (3/3)	💚 2.857
Classes	100.0% (3/3)	💚 2.857
Methods	100.0% (36/36)	💚 10.924
Lines	95.17% (670/704)	👍 5.141
Conditionals	100.0% (0/0)	💚