Added CI for shell script

.gitlab-ci.yml

+image: debian:bullseye-slim
+
+before_script:
+  - apt update -y
+  - apt install -y git make shellcheck golang-go
+  - export GOPATH="$HOME/go"
+  - export PATH="$PATH:$GOPATH/bin"
+  - go get -u github.com/mvdan/sh/cmd/shfmt
+
+linters:
+  script:
+    - make check

Makefile

+SOURCES=./files/start.sh
+LENGTH=96
+
+check: $(SOURCES)
+	shellcheck $^
+	shfmt -i 2 -d $^
+
+format: $(SOURCES)
+	shfmt -i 2 -w $^