Ignore test files in Istanbul coverage reporting

- Added `/* istanbul ignore file */` comment to `Decorators.spec.ts`, `Functions.spec.ts`, `ITSinjex.spec.ts`

src/__tests__/Decorators.spec.ts

@@ -1,3 +1,4 @@
+/* istanbul ignore file */
 /* eslint-disable @typescript-eslint/no-explicit-any */
 import { Inject } from 'src/decorators/Inject';
 import { DependencyResolutionError } from 'src/interfaces/Exceptions';

src/__tests__/Functions.spec.ts

@@ -1,3 +1,4 @@
+/* istanbul ignore file */
 /* eslint-disable @typescript-eslint/no-explicit-any */
 import { ITSinjex, ITSinjex_ } from 'src/interfaces/ITSinjex';
 

src/__tests__/ITSinjex.spec.ts

@@ -1,3 +1,4 @@
+/* istanbul ignore file */
 import { ITSinjex_, ITSinjex } from '../interfaces/ITSinjex';
 
 /**