feat: add support for additional tags

[Gezi-lzq]

• Add additional_tags variable to allow external tag specification
• Implement common_tags local variable to merge default and additional tags
• Update all resources to use centralized tag management
• Add usage example in README for additional_tags feature

This enables users to add custom tags like Environment, Project, Owner, etc. to all AWS resources created by this module.

[Copilot]

Pull Request Overview

This PR adds support for additional tags to be applied to all AWS resources created by the module. Users can now specify custom tags through the additional_tags variable, which are merged with the default tags (automqVendor and automqEnvironmentID) and applied consistently across all resources.

• Added additional_tags variable to enable external tag specification
• Implemented centralized tag management using a common_tags local variable
• Updated all resource tag definitions to use the centralized tagging approach

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
variables.tf	Added additional_tags variable definition
main.tf	Updated EC2 instance and EBS volume resources to use centralized tagging
aws.tf	Implemented common_tags local variable and updated all AWS resources to use centralized tagging
README.md	Added usage example demonstrating the additional_tags feature

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