Integrate shellcheck in CI

.circleci/config.yml

@@ -11,7 +11,7 @@ jobs:
       - run:
           command: |
             apt update -qq
-            apt install -y --no-install-recommends software-properties-common wget gpg-agent
+            apt install -y --no-install-recommends software-properties-common wget gpg-agent shellcheck
             apt-add-repository -y ppa:jonathonf/gcc-9.1
             wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|apt-key add -
             apt-add-repository -y "deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-8 main"
@@ -50,6 +50,8 @@ jobs:
             echo
             echo "########## clang-tidy-8 ##########"
             clang-tidy-8 src/* -- -I/usr/include -I/usr/include/ncursesw
+            echo "########## checllcheck ##########"
+            find plugins/ -type f -not -name "*.md" -exec shellcheck -e SC1090 {} +
 
   package-and-publish:
     machine: true