Add version Nim 2.2.0 to CI tests

Author: treeform

.github/workflows/build.yml

@@ -6,7 +6,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        nim-version: ['1.4.0', '1.4.x', '1.6.x', 'stable']
+        nim-version: ['1.4.0', '2.2.0', '2.0.12', 'stable']
 
     runs-on: ${{ matrix.os }}