docs(angular): add language service content (#6363)

src/data/roadmaps/angular/content/language-service@ql7SyxrRmjpiXJ9hQeWPq.md

@@ -1 +1,8 @@
 # Language Service
+
+The Angular Language Service provides code editors with a way to get completions, errors, hints, and navigation inside Angular templates (external and in-line). Anytime you open an Angular application for the first time, an installation prompt will occur.
+
+Visit the following links to learn more:
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+- [@official@Language Service Docs](https://angular.dev/tools/language-service)
+- [@opensource@VS Code NG Language Service](https://github.com/angular/vscode-ng-language-service)