chore: optimize README for clarity and conciseness

[h2zi]

• Do only one thing
• Non breaking API changes
• Tested

What did this pull request do?

This pull request updates the README.md to improve clarity, provide better documentation, and introduce alternatives for users who require a CGO-free SQLite driver.

Documentation improvements:

• Updated the title and introductory section to clarify that this is the official SQLite driver for GORM, and added a link to the GORM documentation.
• Enhanced the usage section with a clearer "Quick Start" example and provided a direct link to the full documentation.

Alternative driver information:

• Added a new section listing pure Go (CGO-free) alternatives to the default driver, including a comparison table and example usage for swapping the import path.

Other improvements:

• Updated the CI badge to be clickable, linking directly to GitHub Actions.

User Case Description

• Clearly states that the official driver requires CGO, helping developers quickly assess compatibility with their build environment.
• Consolidates duplicated pure Go driver sections into a single, well-structured comparison, reducing confusion.
• Provides a one-line project description so the purpose of the repository is immediately apparent.
• Makes the CI badge clickable for quick access to build status.

[Copilot]

Pull request overview

Updates README.md to make the repository’s purpose and usage clearer, and to document CGO-free SQLite driver alternatives for GORM users.

Changes:

• Clarified the README title/intro and added a concise “official driver” description (including CGO requirement).
• Reworked the usage section into a “Quick Start” with a pointer to full docs.
• Consolidated CGO-free alternatives into a single section with a comparison table and import-swap guidance; made the CI badge clickable.

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