Add option to decode CBOR bignum to `interface{}` as `*big.Int` #505

	# GitHub Actions - CI for Go to build & test.
	# https://github.com/fxamacker/cbor/workflows/ci.yml
	# See ci-go-cover.yml for coverage and safer-golangci-lint.yml for linting.
	name: ci

	# Revoke default permissions.
	permissions: {}

	on:
	workflow_dispatch:
	pull_request:
	push:
	branches:
	- 'master'
	- 'release*'
	- 'feature/stream-mode'
	tags:
	- 'v*'
	jobs:
	# Test on various OS with default Go version.
	tests:
	name: test ${{matrix.os}} go-${{ matrix.go-version }}
	runs-on: ${{ matrix.os }}
	permissions:
	contents: read
	strategy:
	matrix:
	os: [macos-latest, ubuntu-latest, windows-latest]
	go-version: [1.17, 1.19, '1.20', 1.21]
	steps:
	- name: Install Go
	uses: actions/setup-go@93397bea11091df50f3d7e59dc26a7711a8bcfbe # v4.1.0
	with:
	go-version: ${{ matrix.go-version }}
	check-latest: true

	- name: Checkout code
	uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
	with:
	fetch-depth: 1

	- name: Print Go version
	run: go version

	- name: Get dependencies
	run: go get -v -t -d ./...

	- name: Build project
	run: go build ./...

	- name: Run tests
	run: \|
	go version
	go test -race -v ./...

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