[ci] Update to `actions/checkout` `v4` from `v3`. #1077

	on:
	pull_request:
	push:
	branches:
	- master
	tags:
	- "*"

	name: Continuous integration

	jobs:
	check:
	name: Rustfmt
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v4
	- uses: dtolnay/rust-toolchain@stable
	- run: rustup component add rustfmt

	- name: rustfmt check
	run: cargo fmt --all -- --check

	clippy-lint:
	name: Clippy lints
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v4
	- name: install stable toolchain
	uses: dtolnay/rust-toolchain@stable

	- name: install druid dependencies
	run: \|
	sudo apt update
	sudo apt install libpango1.0-dev libxkbcommon-dev libxkbcommon-x11-dev

	- run: git submodule update --init --recursive

	- name: cargo clippy
	run: cargo clippy --all-targets -- -D warnings

	- name: cargo clippy --all-features
	run: cargo clippy --all-features --all-targets -- -D warnings

	- name: cargo doc
	run: cargo doc --all-features --document-private-items --no-deps
	env:
	RUSTDOCFLAGS: -D warnings


	test-stable:
	runs-on: ${{ matrix.os }}
	strategy:
	matrix:
	os: [ubuntu-latest, windows-latest]

	name: cargo test stable
	steps:
	- uses: actions/checkout@v4

	- name: install stable toolchain
	uses: dtolnay/rust-toolchain@stable

	- name: install druid dependencies
	run: \|
	sudo apt update
	sudo apt install libpango1.0-dev libxkbcommon-dev libxkbcommon-x11-dev
	if: contains(matrix.os, 'ubuntu')

	- run: git submodule update --init --recursive

	- name: cargo test
	run: cargo test

	- name: cargo test --all-features
	run: cargo test --all-features

Provide feedback