Test multiple Elixir versions on CI

Author: ankane

.github/workflows/build.yml

@@ -3,12 +3,16 @@ on: [push, pull_request]
 jobs:
   build:
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        elixir: [1.19, 1.18, 1.13]
     steps:
       - uses: actions/checkout@v4
       - uses: erlef/setup-beam@v1
         with:
           otp-version: 27
-          elixir-version: 1.18
+          elixir-version: ${{ matrix.elixir }}
       - run: mix deps.get
       - uses: ankane/setup-postgres@v1
         with: