docs: add PR template and CONTRIBUTING.md guide; minor README tweaks #49

	name: Tests
	on: [push, pull_request]
	env:
	GOVERSION: "1.21"
	jobs:
	test:
	name: Check code quality and run tests
	if: "!contains(github.event.head_commit.message, '[ci skip]')"
	runs-on: ubuntu-latest
	steps:
	- name: Set up Go
	uses: actions/setup-go@v5
	with:
	go-version: ${{env.GOVERSION}}

	- name: Check out code
	uses: actions/checkout@v4

	- name: Run gofmt
	run: test -z "$(gofmt -s -d *.go 2>&1)"

	- name: Run golint
	run: go install golang.org/x/lint/golint@latest && golint -set_exit_status

	- name: Run go vet
	run: go vet

	- name: Run tests
	run: go test -v -coverprofile=coverage.out -covermode=count

	- name: Report coverage
	env:
	COVERALLS_TOKEN: ${{ secrets.GITHUB_TOKEN }}
	run: go install github.com/mattn/goveralls@latest && goveralls -coverprofile=coverage.out -service=github
	continue-on-error: true

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