Refactor CI workflow (#43)

## Description

This PR renames and refactors the project's GitHub Actions CI workflow.
The updated workflow will now run on:

- pushes to `main`,
- pull requests against `main`, and
- by manual invocation via GitHub's UI

Notable changes to the workflow include:

- refactors existing Ubuntu test job
- adds a new macOS test job
- specifies oldest and newest Elixir and Erlang combo in the matrix
- use latest [actions/checkout](https://github.com/actions/checkout)
- sets job name to use matrix values for clarity

The macOS job takes a necessarily different tact for installing Erlang
and Elixir owing to the underlying `erlef/setup-beam` workflow not (yet)
supporting macOS (see erlef/setup-beam#54).

.github/workflows/ci.yml

@@ -0,0 +1,74 @@
+name: CI
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+  workflow_dispatch:
+
+env:
+  MIX_ENV: test
+
+jobs:
+  test_macos:
+    name: Elixir ${{ matrix.pair.elixir }} OTP ${{ matrix.pair.otp }} (macOS)
+    runs-on: macos-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        pair:
+          - elixir: "1.13"
+            otp: "24.3.4.10"
+          - elixir: "1.17"
+            otp: "27.0.1"
+    steps:
+      - uses: actions/checkout@v4
+      - name: Generate .tool-versions file
+        run: |
+          echo "elixir ${{ matrix.pair.elixir }}" >> .tool-versions
+          echo "erlang ${{ matrix.pair.otp }}" >> .tool-versions
+          cat .tool-versions
+      - uses: asdf-vm/actions/install@v3
+      - name: Install Hex package manager
+        run: mix local.hex --force
+      - name: Install dependencies
+        run: mix deps.get
+      - run: mix test
+  test_ubuntu:
+    name: Elixir ${{ matrix.pair.elixir }} OTP ${{ matrix.pair.otp }} (Ubuntu)
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - pair:
+              elixir: "1.13"
+              otp: "24.3.4.10"
+          - pair:
+              elixir: "1.17"
+              otp: "27.0.1"
+            lint: lint
+    steps:
+      - uses: actions/checkout@v4
+      - uses: erlef/setup-beam@main
+        with:
+          otp-version: ${{ matrix.pair.otp }}
+          elixir-version: ${{ matrix.pair.elixir }}
+          version-type: strict
+      - uses: actions/cache@v4
+        with:
+          path: deps
+          key: mix-deps-${{ hashFiles('**/mix.lock') }}
+      - run: mix deps.get --check-locked
+      - run: mix format --check-formatted
+        if: ${{ matrix.lint }}
+      - run: mix deps.unlock --check-unused
+        if: ${{ matrix.lint }}
+      - run: mix deps.compile
+      - run: mix compile --warnings-as-errors
+        if: ${{ matrix.lint }}
+      - run: mix test
+        if: ${{ ! matrix.lint }}
+      - run: mix test --warnings-as-errors
+        if: ${{ matrix.lint }}

README.md

@@ -1,6 +1,6 @@
 # DartSass
 
-[![CI](https://github.com/CargoSense/dart_sass/actions/workflows/main.yml/badge.svg)](https://github.com/CargoSense/dart_sass/actions/workflows/main.yml)
+[![CI](https://github.com/CargoSense/dart_sass/actions/workflows/ci.yml/badge.svg)](https://github.com/CargoSense/dart_sass/actions/workflows/ci.yml)
 
 Mix tasks for installing and invoking [sass](https://github.com/sass/dart-sass/).