Updated Contrib (markdown)

Contrib.md

@@ -2,3 +2,25 @@ This page lists various tips, tricks and user contributions. Feel free to add to
 
 * [[Recursiveness]]: Tips for running ShellCheck on all scripts in a directory
 * [[CentOS6]] and [[More-Installation-Guides]] for installing ShellCheck on CentOS 6 
+
+
+### Docker wrapper script
+
+[@jrupp says](https://github.com/koalaman/shellcheck/issues/1126):
+
+I wrote a script to add shellcheck to any system running docker, without actually installing anything. I put this into `/usr/local/bin/shellcheck`:
+
+```sh
+#!/bin/bash -
+for last; do true; done
+docker run --rm -iv "$( cd "$( dirname -- "${last}" )" && pwd )":/mnt koalaman/shellcheck "${@:1:$(($#-1))}" "$(basename -- "${last}")"
+```
+
+This works on Docker for Mac as well as a linux system running docker.  I have tested it when calling shellcheck in any of these forms:
+
+- `shellcheck filename.sh`
+- `shellcheck ../../filename.sh`
+- `cat filename.sh | shellcheck -`
+- `shellcheck -V`
+
+No modification of my editor settings was needed for this to integrate (I checked Vim through syntastic and VSCode).