Apply suggestions from code review

Co-authored-by: Brian Smith <[email protected]>

files/en-us/glossary/source_map/index.md

@@ -15,6 +15,7 @@ Code executed by the browser is often transformed in some way from the original
 - To use languages that browsers don't support, like {{Glossary("TypeScript")}} or [Sass](https://sass-lang.com/).
 
 In these situations, debugging the original source is much easier than the source in the transformed state that the browser has downloaded.
+Browsers detect a source map via the {{HTTPHeader("SourceMap")}} HTTP header for a resource, or a `sourceMappingURL` annotation in the generated code. 
 
 ## Example