feat: Disable language service for non-Angular projects
feat: Disable language service for non-Angular projects

Disable the langauge service for a particular project if it is not an
Angular project.
The detection mechanism relies on the presence of
`@angular/core/core.d.ts` file in the program.

PR closes https://github.com/angular/vscode-ng-language-service/issues/391

angular/vscode-ng-language-service,angular/vscode-ng-language-service,angular/vscode-ng-language-service,angular/vscode-ng-language-service