[CI] Add Clang 11 to the build matrix.

Author: vyazelenko

.github/workflows/ci.yml

@@ -126,7 +126,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        version: [ '6.0', '7', '8', '9', '10' ]
+        version: [ '6.0', '7', '8', '9', '10', '11' ]
     env:
       CC: clang-${{ matrix.version }}
       CXX: clang++-${{ matrix.version }}