fix!: resolve memory leaks in receiveMessage and response body handling

[fgiova]

• Cache receiveMessage clients instead of creating/closing one per call, preventing connection churn and potential leaks
• Dump response body on non-JSON responses to avoid undrained socket leaks
• Destroy cached receiveMessage clients in destroy() method
• Drop Node.js 20 support, require ^22.14.0 || >= 24.10.0
• Upgrade @fgiova/aws-signature to ^4.0.0, undici to ^7.21.0
• Update CI matrix and release workflow (Node 22/24 only, OIDC permissions)
• Fix README badges, usage example and API signatures

BREAKING-CHANGE: Drop support to Node.js 20.x

[Copilot]

Pull request overview

This PR addresses connection/body handling leaks by reusing receiveMessage clients, draining non-JSON response bodies, and aligning project/runtime/tooling with Node 22/24.

Changes:

• Cache receiveMessage HTTP clients and destroy them in MiniSQSClient.destroy()
• Drain response bodies for non-JSON responses to avoid socket leaks
• Drop Node 20 support and update dependencies/CI/docs accordingly

Reviewed changes

Copilot reviewed 6 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/index.ts	Adds a cached undici Client for receiveMessage, drains bodies on non-JSON responses, and destroys cached clients on destroy()
test/index.ts	Adds a test intended to cover cached receiveMessage client behavior
package.json	Updates Node engine range and bumps @fgiova/aws-signature + undici versions
README.md	Updates badges, Node requirements, and usage/API signature examples
.nvmrc	Updates default Node version to 22
.gitignore	Ignores /.claude/
.github/workflows/node.js.yml	Updates CI matrix to Node 22/24 and adjusts permissions/coverage/release steps

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[Copilot]

The release job no longer has the push-only guard (previously if: github.event_name == 'push'). Since this workflow also runs on pull_request, the release job can execute on PR events, which is risky for publishing. Reintroduce an if: condition (e.g., github.event_name == 'push' and/or github.ref == 'refs/heads/main') to ensure releases only run on intended events/branches.