Add MR widget error count to test reports docs

doc/ci/junit_test_reports.md

@@ -42,13 +42,15 @@ JUnit test reports, where:
 - The base branch is the target branch (usually `master`).
 - The head branch is the source branch (the latest pipeline in each merge request).
 
-The reports panel has a summary showing how many tests failed and how many were fixed.
-If no comparison can be done because data for the base branch is not available,
-the panel will just show the list of failed tests for head.
+The reports panel has a summary showing how many tests failed, how many had errors
+and how many were fixed. If no comparison can be done because data for the base branch
+is not available, the panel will just show the list of failed tests for head.
 
-There are three types of results:
+There are four types of results:
 
 1. **Newly failed tests:** Test cases which passed on base branch and failed on head branch
+1. **Newly encountered errors:** Test cases which passed on base branch and failed due to a
+   test error on head branch
 1. **Existing failures:**  Test cases which failed on base branch and failed on head branch
 1. **Resolved failures:**  Test cases which failed on base branch and passed on head branch