shellcheck: add page (#2140)

pages/common/shellcheck.md

@@ -0,0 +1,19 @@
+# shellcheck
+
+> Shell script static analysis tool.
+
+- Check a shell script:
+
+`shellcheck {{file.sh}}`
+
+- Override script's shebang:
+
+`shellcheck --shell {{sh|bash|ksh}} {{file.sh}}`
+
+- Ignore certain errors:
+
+`shellcheck --exclude {{SC1009}} {{file.sh}}`
+
+- Ignore multiple errors:
+
+`shellcheck --exclude {{SC1009,SC1073}} {{file.sh}}`