Formatting, new image and Nav location

Signed-off-by: Tom Daykin <tdaykin@live.co.uk>

docs/guides/github/contributing.md

@@ -17,6 +17,10 @@ Contributors *sign-off* that they adhere to these requirements by adding a Signe
 
 #### DCO Failures
 
+The Pi-hole project uses a DCO bot for all GitHub pulls to verify that each commit is signed off. When you create your pull request, it will automaticaly be verified by this bot. An example of what to expect is below.
+
+![Screenshot](../../images/github-commit-bots.png)
+
 If your Pull Request fails the DCO check, it's necessary to fix the entire commit history in the PR. Although this is a situation we'd like to avoid the best practice is to squash the commit history to a single commit, append the DCO sign-off as described above or interactively in the rebase comment editing process, and force push. For example, if you have 2 commits in your history (Note the ~2):
 
 ```bash

docs/guides/github/how-to-signoff.md

@@ -4,11 +4,11 @@ This is my commit message
 
 Signed-off-by: Random J Developer <random@developer.example.org>
 ```
-The text can either be manually added to your commit body, or you can add either -s or --signoff to your usual git commit commands. 
+The text can either be manually added to your commit body, or you can add either `-s` or `--signoff` to your usual git commit commands. 
 
 #### Creating your signoff
 
-Git has a -s | --signoff command line option to append this automatically to your commit message:
+Git has a `-s | --signoff` command line option to append this automatically to your commit message:
 
 ```$ git commit --signoff --message 'This is my commit message'```