chore: only accept CSV files

Author: ghiscoding

src/app/examples/grid43.component.ts

@@ -21,14 +21,16 @@ export class Grid43Component {
   constructor(private readonly cd: ChangeDetectorRef) {}
 
   handleFileImport(event: any) {
-    const file = event.target.files[0];
-    if (file) {
+    const file: File = event.target.files[0];
+    if (file.name.endsWith('.csv')) {
       const reader = new FileReader();
       reader.onload = (e: any) => {
         const content = e.target.result;
         this.dynamicallyCreateGrid(content);
       };
       reader.readAsText(file);
+    } else {
+      alert('File must be a CSV file');
     }
   }