Add contributing blob to footer.

content/_footer.md

@@ -3,3 +3,5 @@
 +++
 
 {{< icon name="copyright-mark" >}} [Holland Computing Center] (https://hcc.unl.edu) | 118 Schorr Center, Lincoln NE 68588 | {{< icon name="envelope" >}}[hcc-support@unl.edu] (mailto:hcc-support@unl.edu) | {{< icon name="phone-alt" >}}402-472-5041
+
+See something wrong?  Help us fix it by [contributing](https://git.unl.edu/hcc/hcc-docs/blob/master/CONTRIBUTING.md)!