Add test case parsing limit and node limit

doc/ci/unit_test_reports.md

@@ -350,6 +350,11 @@ If parsing JUnit report XML results in an error, an indicator is shown next to t
 
 ![Test Reports With Errors](img/pipelines_junit_test_report_with_errors_v13_10.png)
 
+NOTE:
+GitLab.com has a 500,000 [test case parsing limit](../user/gitlab_com/#gitlab-cicd). Self-managed administrators can manage this setting on their instance.
+
+GitLab does not parse very [large nodes](https://nokogiri.org/tutorials/parsing_an_html_xml_document.html#parse-options) of JUnit reports. There is [an issue](https://gitlab.com/gitlab-org/gitlab/-/issues/268035) open to make this optional.
+
 ## Viewing JUnit screenshots on GitLab
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/202114) in GitLab 13.0 behind the `:junit_pipeline_screenshots_view` feature flag, disabled by default.