Add new page "Add iOS devices" to PR 190

[tungmhoang]

Tasks:

• Check out the PR: https://github.com/kobiton/docs/pull/190
• Add a new page under docs/modules/device-lab-management/pages/ios-devices/. Fill in the new page with this content: KOBITON-Add iOS devices-300524-091231.pdf
• At the start of the pdf file there is a link to the prepare an iOS device page. Link that to our new page at docs/modules/device-lab-management/pages/android-devices/prepare-ios-device.adoc
• If there are links that points to current page on docs.kobiton.com, use xref to reference accordingly.

[Hikkigaya]

@tungmhoang task completed and pushed to the repository.