CI housekeeping

List of changes:
- add min and max Elixir/Erlang matrix
- add more CI tasks
- bump GitHub actions

.github/workflows/ci.yml

@@ -8,26 +8,47 @@ on:
 
 jobs:
   build:
-    name: Build and test
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
+    strategy:
+      matrix:
+        include:
+          - pair:
+              elixir: 1.14.x
+              otp: 23.x
+          - pair:
+              elixir: 1.17.x
+              otp: 27.x
+            lint: lint
+
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
-      - name: Set up Elixir
-        uses: erlef/setup-beam@v1
+      - uses: erlef/setup-beam@v1
         with:
-          otp-version: "25.3"
-          elixir-version: "1.14"
+          otp-version: ${{matrix.pair.otp}}
+          elixir-version: ${{matrix.pair.elixir}}
 
-      - name: Restore dependencies cache
-        uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
-          path: deps
-          key: ${{ runner.os }}-mix-${{ hashFiles('**/mix.lock') }}
-          restore-keys: ${{ runner.os }}-mix-
-
-      - name: Install dependencies
-        run: mix deps.get
-      - name: Run tests
-        run: mix test
+          path: |
+            deps
+            _build
+          key: ${{ runner.os }}-mix-${{matrix.pair.elixir}}-${{matrix.pair.otp}}-${{ hashFiles('**/mix.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-mix-${{matrix.pair.elixir}}-${{matrix.pair.otp}}-
+
+      - run: mix deps.get
+
+      - run: mix format --check-formatted
+        if: ${{ matrix.lint }}
+
+      - run: mix deps.get && mix deps.unlock --check-unused
+        if: ${{ matrix.lint }}
+
+      - run: mix deps.compile
+
+      - run: mix compile --warnings-as-errors
+        if: ${{ matrix.lint }}
+
+      - run: mix test