QoL: Add Package Manager Support Across Multiple Platforms

> NOTE: This should likely be done after the alpha phase, and definitely in multiple PRs for each package manager.
> As a QoL improvement this is a *nice to have* not a *must have*

#### Problem

Users currently need to install the EigenLayer DevKit by downloading precompiled binaries. This creates a suboptimal experience, especially for users who rely on package managers to handle dependency resolution and installation. Adding proper support across major platforms would improve accessibility, reduce onboarding friction, and align with current developer tooling conventions.

#### Solution

Create official packages for major platform package managers, including:

* Homebrew (macOS/Linux)
* Arch Linux AUR
* Debian/Ubuntu Snapcraft or Apt repository
* Fedora (DNF)

#### Motivation

This change would significantly improve the developer experience by:

1. Providing a standard way to install the EigenLayer DevKit via familiar package managers

### Expected Outcome

1. **Installation Experience**
- Users should be able to install the DevKit using their preferred package manager without significant configuration changes

```
# macOS/Linux:
$ brew install eigen-devkit

# Arch Linux:
$ yay -S eigen-devkit
```

> A good reference for how users of other linux distributions are familiar with installing third-party pacakges would be the Brave Browser installation instructions for linux: https://brave.com/linux/

2. **Documentation**
- All package installation methods must be documented in `README.md`
- The README should include a "Package Manager Installation" section

### Additional Notes

1. This feature requires maintaining multiple package definitions simultaneously
2. There should be a `contrib/` directory at the root of the repository containing all package definitions

### Implementation Approach

1. **Phase 1: Research**
- Investigate official package manager interfaces for each platform
- Create initial draft packages

2. **Phase 2: Initial Implementation**
- Write and test the package definitions

3. **Phase 3: Integration**
- Add CI workflows to build and test packages
- Update project documentation

### Resources

1. [Homebrew Formula Guide](https://docs.brew.sh/Formula-Cookbook)
2. [Arch Linux Packaging](https://wiki.archlinux.org/title/Creating_packages)
3. [Debian Packaging](https://wiki.debian.org/HowToPackageForDebian)
4. [Fedora Packaging Tutorial](https://docs.fedoraproject.org/en-US/package-maintainers/Packaging_Tutorial/)

README.md と、ルートレベルに提案されている contrib/ ディレクトリから始め、次に issue からリンクされている Homebrew、Arch、Debian、Fedora のパッケージングに関するリファレンスを確認します。パッケージマネージャーの対象範囲と、各パッケージが既存の DevKit をどのようにインストールするかを定義します。完了条件は、パッケージ定義、それらをビルドしてテストする CI ワークフロー、および新しい README セクションに記載されたインストール方法が揃っていることです。

索引モデルが issue の本文から書いたものです。