Add README content (microsoft#2)

* Add Purpose section

* Add Usage section

* Add Notes section

* Remove "/en-us" from doc links

README.md

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+# Updating Azure PowerShell modules in Azure Automation accounts
 
-# Contributing
+## Purpose
+
+This Azure Automation runbook updates Azure PowerShell modules imported into an Azure Automation
+account with the module versions published to the PowerShell Gallery. See
+[How to update Azure PowerShell modules in Azure Automation](https://docs.microsoft.com/azure/automation/automation-update-azure-modules)
+for more details.
+
+## Usage
+
+Import this runbook into your Automation account, and [start](https://docs.microsoft.com/azure/automation/automation-starting-a-runbook) it as a regular Automation runbook.
+
+## Notes
+
+* If you import this runbook with the original name (**Update-AutomationAzureModulesForAccount**),
+  it will override the internal runbook with this name. As a result, the imported runbook will
+  run when the **Update Azure Modules** button is pushed or when this runbook is invoked directly
+  via ARM API for this Automation account. If this is not what you want, specify a different name
+  when importing this runbook.
+* Only **Azure** and **AzureRM.\*** modules are currently supported. The new [Azure PowerShell Az modules](https://docs.microsoft.com/powershell/azure/new-azureps-module-az) are not supported yet.
+  Avoid starting this runbook on Automation accounts that contain Az modules.
+* Before starting this runbook, make sure your Automation account has an [Azure Run As account credential](https://docs.microsoft.com/azure/automation/manage-runas-account) created.
+* You can use this code as a regular PowerShell script instead of a runbook: just login to Azure
+  using the [Connect-AzureRmAccount](https://docs.microsoft.com/powershell/module/azurerm.profile/connect-azurermaccount)
+  command first, then pass `-Login $false` to the script.
+* To use this runbook on the sovereign clouds, provide the appropriate value to the `AzureEnvironment`
+  parameter. Please also make sure you read the
+  [compatibility notes](https://docs.microsoft.com/azure/automation/automation-update-azure-modules#alternative-ways-to-update-your-modules).
+* When facing compatibility issues, you may want to use specific older module versions instead of
+  the latest available on the PowerShell Gallery. In this case, provide the required versions in
+  the `ModuleVersionOverrides` parameter.
+
+## Contributing
 
 This project welcomes contributions and suggestions.  Most contributions require you to agree to a
 Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us