code refactoring

src/app/models/post.model.ts

@@ -3,7 +3,7 @@ export interface IPost{
     slug: string;
     title: string;
     description: string;
-    categories: string;
+    categories: string[];
     postUrl: string;
     likes: number;
     views: number;

src/app/models/project.model.ts

@@ -2,7 +2,7 @@ export interface IProject{
     projectId: number;
     name: string;
     description: string;
-    categories: string;
+    categories: string[];
     categoryList: string[];
     roles: string[];
     responsibilities: string[];