Add additional-theme option #1349

	name: CI
	on:
	# Only run when merging to master, or open/synchronize/reopen a PR.
	push:
	branches:
	- master
	pull_request:

	jobs:
	test:
	name: Test
	runs-on: ${{ matrix.os }}
	strategy:
	matrix:
	build: [stable, beta, nightly, macos, windows, msrv]
	include:
	- build: stable
	os: ubuntu-latest
	rust: stable
	- build: beta
	os: ubuntu-latest
	rust: beta
	- build: nightly
	os: ubuntu-latest
	rust: nightly
	- build: macos
	os: macos-latest
	rust: stable
	- build: windows
	os: windows-latest
	rust: stable
	- build: msrv
	os: ubuntu-20.04
	# sync MSRV with docs: guide/src/guide/installation.md and Cargo.toml
	rust: 1.60.0
	steps:
	- uses: actions/checkout@v3
	- name: Install Rust
	run: bash ci/install-rust.sh ${{ matrix.rust }}
	- name: Build and run tests
	run: cargo test --locked
	- name: Test no default
	run: cargo test --no-default-features

	rustfmt:
	name: Rustfmt
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v3
	- name: Install Rust
	run: rustup update stable && rustup default stable && rustup component add rustfmt
	- run: cargo fmt --check

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