aggregate parameter in CI strategy

Author: tribbloid

.github/workflows/main.yml

@@ -18,7 +18,7 @@ jobs:
     needs: vars
     runs-on: ubuntu-latest
 
-    strategy:
+    strategy: &scala_strategy
       max-parallel: 2
       fail-fast: false
       matrix:
@@ -50,11 +50,7 @@ jobs:
     runs-on: ubuntu-latest
 
     #TODO: don't repeat yourself
-    strategy:
-      max-parallel: 2
-      fail-fast: false
-      matrix:
-        scalaVersion: ["2.13.9", "2.13.10", "2.13.11", "2.13.12", "2.13.13", "2.13.14", "2.13.15", "2.13.16", "2.13.17", "2.13.18"]
+    strategy: *scala_strategy
 
     continue-on-error: ${{ contains(needs.vars.outputs.experimentalScalaVersions, matrix.scalaVersion) }}