Add images for Key Vault and Storage Account in walkthrough challenge 2

[janegilring]

This pull request updates the Azure Key Vault and Storage Account walkthrough documentation to improve clarity, user guidance, and visual support. The most important changes include reorganizing resource group creation steps, updating portal navigation instructions, and replacing external image links with local images for better reliability. These changes make the instructions easier to follow and more robust for users.

Documentation improvements and reorganization:

• Clarified resource group creation instructions, specifying that this step is only needed for non-Microsoft-hosted events, and improved the hash generation step description.
• Updated portal navigation instructions for both Key Vault and Storage Account encryption steps to reflect the current Azure portal UI, making it easier for users to locate settings. [1] [2]

Visual and instructional enhancements:

• Replaced external image links with local image references for Key Vault and Storage Account steps, ensuring images are reliably available and improving visual guidance. [1] [2] [3]
• Added instructions to wait for backend consistency after assigning managed identity to the storage account, reducing potential errors in subsequent steps.

Cleanup and consistency:

• Removed redundant image links and improved formatting throughout the walkthrough for a cleaner, more consistent user experience. [1] [2] [3] [4] [5]