Docs: Add License

[nick-y-ito]

Overview

This PR aims to add an OSS license to this repository.

Changes

• Added the LICENSE file to the root directory
• Added the License section to README.md
• Added the Nishiki logo to the bottom of README.md (extra)

Screen Captures

I have added in this flow:

References

• https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/licensing-a-repository#determining-the-location-of-your-license

Notes

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]

@kanta1207 @ShoeheyOt @kotaaaa Could you please review this PR when you have a moment?

[nick-y-ito]

@kanta1207 Thank you for your review!😄