[docs] Update IIS README to use documentation guidelines

[colleenmcginnis]

Proposed commit message

Update README to use documentation guidelines

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

• @colleenmcginnis Initial draft to align with the documentation guidelines
• @SubhrataK to provide an initial review of the structure
• @colleenmcginnis address initial feedback, remove draft status
• @elastic/obs-infraobs-integrations technical review
• @colleenmcginnis address additional feedback, merge

How to test this PR locally

View the README.

Related issues

Related to elastic/observability-docs#3270

[elasticmachine]

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• Start Time: 2023-10-30T19:08:38.155+0000

• Duration: 14 min 47 sec

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Test	Results
Failed	0
Passed	29
Skipped	0
Total	29

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (2/2)	💚
Files	100.0% (2/2)	💚
Classes	100.0% (2/2)	💚
Methods	86.111% (31/36)	❕
Lines	96.143% (349/363)	❕
Conditionals	100.0% (0/0)	💚

[SubhrataK]

Looks good!

[shmsr]

Thank you for improving the documentation 🎉

[elasticmachine]

Package iis - 1.17.1 containing this change is available at https://epr.elastic.co/search?package=iis