docs(rsc): combine canary/experimental and react-server-dom-webpack sections

[Copilot]

Addresses feedback from #524 (comment)

Changes

Updated the plugin-rsc README to better explain how to use React canary and experimental versions after PR #915 enabled using locally installed react-server-dom-webpack.

What changed

1. Renamed and expanded "Canary and Experimental channel releases" → "Using React Canary and Experimental versions"

   • Now presents two clear options for using canary/experimental React
   • Option 1: Use preview releases from pkg.pr.new (chore(rsc): release for react canary/experimental channel [not merge] #524)
   • Option 2: Install react-server-dom-webpack directly - the simpler approach enabled by feat(rsc): use locally installed react-server-dom-webpack when available #915
   • Added concrete package.json examples for both canary and experimental versions

2. Merged "Customizing react-server-dom-webpack" section into Option 2

   • Integrated the content from the standalone "Customizing react-server-dom-webpack" section into Option 2
   • Eliminated duplication by keeping all related information in one place
   • Shows how the plugin automatically uses locally installed react-server-dom-webpack

Why

Before PR #915, users needed to use the pkg.pr.new preview releases (#524) to get canary/experimental React versions. After #915, users can simply install react-server-dom-webpack@canary or @experimental in their own project - a much simpler approach.

The previous documentation had these as separate, disconnected sections. This update combines them to show users both options with clear guidance.

Example

Users can now easily use React canary by adding to their package.json:

{
  "dependencies": {
    "react": "canary",
    "react-dom": "canary",
    "react-server-dom-webpack": "canary"
  }
}

The plugin will automatically use the locally installed version instead of the vendored one.

Original prompt

update plugin-rsc/readme to address #524 (comment)

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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.

[hi-ogawa]

@copilot

• flip option 1 and option 2
• merge "Customizing react-server-dom-webpack" section to the first section's option

[Copilot]

@copilot

• flip option 1 and option 2
• merge "Customizing react-server-dom-webpack" section to the first section's option

Done in 4311fae. Flipped the option order (pkg.pr.new is now Option 1) and merged the "Customizing react-server-dom-webpack" section into Option 2.