Fix ISSUE_TEMPLATE typo s/sumbitting/submitting/

Signed-off-by: Chris Swan <478926+cpswan@users.noreply.github.com>

Author: cpswan

.github/ISSUE_TEMPLATE/bug_report.md

@@ -5,7 +5,7 @@ about: Create a report to help us improve
 
 ### Troubleshooting
 
-Before sumbitting a bug report please read the [Troubleshooting doc](https://github.com/docker/build-push-action/blob/master/TROUBLESHOOTING.md).
+Before submitting a bug report please read the [Troubleshooting doc](https://github.com/docker/build-push-action/blob/master/TROUBLESHOOTING.md).
 
 ### Behaviour