Highlight some basic markdown elements in js/ts fenced code blocks

Fixes #63942

extensions/typescript-basics/package.json

@@ -77,6 +77,16 @@
           "meta.import string.quoted": "other",
           "variable.other.jsdoc": "other"
         }
+      },
+      {
+        "scopeName": "documentation.markdown.injection",
+        "path": "./syntaxes/MarkdownDocumentationInjection.tmLanguage.json",
+        "injectTo": [
+          "source.ts",
+          "source.tsx",
+          "source.js",
+          "source.js.jsx"
+        ]
       }
     ],
     "snippets": [