Docs: Add the "Tech Stack" section to "README.md"

[nick-y-ito]

Overview

This PR adds the "Tech Stack" section to "README.md"

Review points

• Is there anything wrong or missing?

Notes

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Assignee Checklist:

• [x] The naming convention of the PR title is correct (See the comment at the top of this template)
• [x] The base branch is correct (See: Types of Branches)
• [x] The branch name follows the Branch Naming Conventions
• [x] The correct assignees and reviewers have been designated for this PR
• [x] The coding style follows the Coding Style Guide
• [x] All the related issues are associated with this PR
• [x] All criteria in the associated issues are met (please tick the checkboxes)
• [x] My changes do not generate new warnings or errors (especially in the console)

Reviewer Checklist:

• [ ] Double-check the "Assignee Checklist"
• [ ] The code follows the generic best practices and our Coding Style Guide
• [ ] The code is well-commented and easy to understand
• [ ] The UI changes accurately reflect the provided design

[nick-y-ito]

Moved to #309