docs: add installation instructions and distribution methods to README

[Copilot]

README contained only a one-line title with no guidance on how to install or use the tool.

Changes

Installation (README.md)

• GitHub Releases — curl one-liners for Linux/macOS (download → chmod +x → move to /usr/local/bin/); Windows instructions to grab renderflow-windows.exe and add to PATH
• Build from source — cargo install --path .

Usage

renderflow build                        # default renderflow.yaml
renderflow build --config custom.yaml   # custom config
renderflow my-project.yaml              # shorthand
renderflow build --dry-run              # preview without output

Includes a clarifying note that the positional argument is always a YAML config file — the Markdown source is declared inside it via input: — to prevent confusion with the renderflow input.md shorthand pattern.

Minimal config example

Shows a working renderflow.yaml stub so users know what to create before running the tool.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>📥 Add installation instructions and distribution methods</issue_title>
<issue_description>### Title: 📥 Add installation instructions and distribution methods

---

Description

Document how users can install and use Renderflow.

---

Goals

• Provide simple install methods
• Improve onboarding experience

---

Requirements

Include instructions for:

• Downloading from GitHub Releases
• Running binary directly
• Optional:

cargo install --path .

• Usage examples:

renderflow input.md

---

Acceptance Criteria

• Instructions clear and concise
• Covers common platforms
• Easy to follow
  </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes 📥 Add installation instructions and distribution methods #47

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Pull Request Summary by devActivity

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