Improve docs

[macie]

Introduces: CONTRIBUTING.md and SECURITY.md files.

[Copilot]

Pull Request Overview

This PR introduces new documentation files to improve contributor guidelines and clarify the project's security policy. It adds SECURITY.md and CONTRIBUTING.md files while updating the README.md to reference the new contributing guidelines and improve language clarity.

• Added SECURITY.md outlining disclosure processes and response timelines.
• Added CONTRIBUTING.md with detailed contribution and code change guidelines.
• Updated README.md for improved clarity and consistency in installation and testing instructions.

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
SECURITY.md	New security policy documentation outlining disclosure methods.
README.md	Updates to installation instructions, algorithm categorization, and pointer to CONTRIBUTING.md.
CONTRIBUTING.md	New contributor guidelines and detailed instructions for adding new sorting algorithms.

Comments suppressed due to low confidence (3)

SECURITY.md:7

• Consider including a brief note on an escalation process or alternative contact method for urgent vulnerability reports, to guide users when the 90-day response timeline may not be sufficient.

Due to limited contributor pool and resources, addressing reported vulnerabilities may take up to 90 days.

README.md:15

• [nitpick] Consider rephrasing the bullet to a more neutral tone, such as 'Algorithms with high time complexity', to avoid subjective or potentially negative language.

- impractical due to poor time complexity:

CONTRIBUTING.md:73

• [nitpick] Clarify in a comment that placeholders like '{Algorithm}' should be replaced with the actual algorithm name to avoid confusion for contributors.

    func {Algorithm}[T constraints.Ordered](ctx context.Context, data []T) error {