[ci] move shellcheck on test-plugins.sh outside test-plugins.sh

It improves reusability of this script

Author: TheTumultuousUnicornOfDarkness

.github/workflows/main.yml

@@ -10,5 +10,8 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
+    - name: Lint test script
+      run: shellcheck ./tests/test-plugins.sh
+
     - name: Run test script
       run: ./tests/test-plugins.sh

tests/test-plugins.sh

@@ -27,11 +27,6 @@ run_invalid_command() {
 	fi
 }
 
-echo -e "\033[1mTesting $0...\033[0m"
-printf "%-60s" " - lint script"
-run_valid_command shellcheck "$(readlink -f "$0")"
-echo
-
 while IFS= read -r -d '' plugin; do
 	name="$(basename "$plugin")"
 	echo -e "\033[1mTesting plugin $name...\033[0m"