Document suppressWarnings config option

[klumhru]

Summary

• Add "Suppressing Compiler Warnings" section to README
• Document suppressWarnings field with example config and generated output
• Explain behavior for each package type (generated vs discovered asmdefs)
• Include table of common warning codes

Test plan

• CI passes (docs-only change)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Documents the suppressWarnings configuration option and how it generates per-assembly csc.rsp files to suppress specific C# compiler warnings in Unity packages.

Changes:

• Add a “Suppressing Compiler Warnings” section to the README with a suppressWarnings example and expected csc.rsp output
• Explain how suppression is applied for raw-mode (generated .asmdef) vs unity-mode (discovered .asmdef) packages
• Include a small table of common warning codes to suppress

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The text says suppressWarnings works with all package types, but the implementation only generates csc.rsp for git-raw, git-unity, and archive packages (raw/unity modes). nuget packages don’t write any csc.rsp (they only extract DLLs), so this section should either exclude nuget from the claim or explicitly state that suppressWarnings is not applicable/ignored for nuget specs.

Suggested change

	The field works with all package types:
	- **`git-raw` / `archive` (raw mode)**: `csc.rsp` is placed in `Runtime/` next to the generated `.asmdef`
	- **`git-unity` / `archive` (unity mode)**: discovers all existing `.asmdef` files in the package and places a `csc.rsp` next to each one
	The field works with all git- and HTTP-archive-based package types:
	- **`git-raw` / `archive` (raw mode)**: `csc.rsp` is placed in `Runtime/` next to the generated `.asmdef`
	- **`git-unity` / `archive` (unity mode)**: discovers all existing `.asmdef` files in the package and places a `csc.rsp` next to each one
	For `nuget` package specs, `suppressWarnings` is currently ignored because the packager only extracts DLLs and does not generate any `csc.rsp` files.