[feature] Optimize activation events

**Is your feature request related to a problem? Please describe.**

The vscode-ng-language-service is activated if html or js files are part of the workspace. This corresponds to nearly all projects.

**Describe the solution you'd like**

Since all angular projects depend on the angular.json file, this file could be used as an activation point and prevent starting the extension in non angular workspaces.

```js
"activationEvents": [
"workspaceContains:**/angular.json"
]
```

**Describe alternatives you've considered**

**Additional context**

The solution should be discussed. I don't know, if it conflicts with other concepts like Angular Elements...

Start by reviewing the vscode-ng-language-service activation configuration and how angular.json is used to identify Angular workspaces. Check whether activation based on angular.json conflicts with Angular Elements or other supported workspace types. Done means the activation rule is agreed, documented, and verified against both Angular and non-Angular workspaces.

Written by the indexing model from the issue text.