Add comprehensive README with features, installation guide, and resources

[Copilot]

The repository lacked detailed documentation about what Sediment is, how to install it, and how to use its features.

Changes

• Project overview: Describes Sediment as an immutable Fedora Atomic Sway desktop with rpm-ostree
• Features: Lists pre-installed software (Docker, Distrobox, Fish shell, kubectl), automatic updates, fingerprint auth, screen capture tools, and bundled fonts
• Installation: ISO download link and step-by-step rebase instructions from existing Fedora Atomic installations
• Getting started: Documents available just commands for fingerprint setup, ASDF installation, JetBrains Toolbox, and screen capture
• System details: Documents custom Sway configs, environment variables, and systemd timer configuration
• Build instructions: Local container build commands using Podman/Buildah
• Resource links: Upstream projects (Fedora Atomic, rpm-ostree, Universal Blue), documentation for included tools, and project resources
• Tips & troubleshooting: Common issues with fingerprint readers, Docker permissions, and immutable OS best practices

The README provides complete onboarding information for new users and serves as technical reference for the system configuration.

Original prompt

create a new readme for this repo, with useful links and startup advice.

Note that you will probably need to do some research in this repo to understand what it is and how it works.

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.