Minor - Add missing doc for github_enterprise_organization and fix typos

[marknet15]

Following on from the awesome work done on #1478 to add organisation creation support, I've just added a missing doc to accompany it and correct some typos.

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Behavior

Before the change?

• The github_enterprise_organization exists but has no reference document.

After the change?

• The PR add the missing document and fixes some typos.

Other information

• N/A

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Additional info

Pull request checklist

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Added the appropriate label for the given change

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes (Please add the Type: Breaking change label)
• No

If Yes, what's the impact:

• N/A

Pull request type

Please add the corresponding label for change this PR introduces:

Type: Documentation

[kfcampbell]

This is great, thank you!