chore: use nim version 2.2.8 (#91)

Author: vil02

.github/workflows/nim_test.yml

@@ -20,7 +20,7 @@ jobs:
           - macos-latest
           - windows-latest
         nim-version:
-          - '2.2.6'
+          - '2.2.8'
 
     steps:
       - uses: actions/checkout@v6