feat(apiclient): Add native Admin & Content API clients, JWT generator, and tag visibility features; remove external @tryghost deps and update docs

ts/classes.tag.ts

@@ -26,6 +26,18 @@ export class Tag {
     return this.tagData.description;
   }
 
+  public getVisibility(): string {
+    return this.tagData.visibility;
+  }
+
+  public isInternal(): boolean {
+    return this.tagData.visibility === 'internal';
+  }
+
+  public isPublic(): boolean {
+    return this.tagData.visibility === 'public';
+  }
+
   public toJson(): ITag {
     return this.tagData;
   }