Grammar Injection - Consider broader Scopes

In order to be able to inject grammar to all language without having to enumerate all of them.

With this, we could use
```json
"grammars": [
     {
     "injectTo": ["source", "text"....]
// ....
}
     ]
```
instead of :
```json
"grammars": [
     {
     "injectTo": ["source.js", "source.ts", "source.jsx", "source.yaml", ....]
// ....
}
     ]
```

src/vs/workbench/services/textMate/electron-browser/TMSyntax.ts

@@ -205,7 +205,13 @@ export class TextMateService implements ITextMateService {
 						return this._scopeRegistry.getFilePath(scopeName);
 					},
 					getInjections: (scopeName: string) => {
-						return this._injections[scopeName];
+						const scopeParts = scopeName.split('.');
+						let injections: string[] = [];
+						for (let i = 1; i <= scopeParts.length; i++) {
+							const subScopeName = scopeParts.slice(0, i).join('.');
+							injections = [...injections, ...this._injections[subScopeName]];
+						}
+						return injections;
 					}
 				});
 				this._updateTheme(grammarRegistry);