support custom script to process delimiter-separated values (data) file / data

src/core/file.ts

@@ -5,6 +5,7 @@ export class KnownFileType {
     public static readonly CSV = new KnownFileType('csv', 'text/csv');
     public static readonly TSV = new KnownFileType('tsv', 'text/tab-separated-values');
     public static readonly MARKDOWN = new KnownFileType('md', 'text/markdown');
+    public static readonly JS = new KnownFileType('js', 'application/javascript');
 
     public readonly extension: string;
     public readonly contentType: string;
@@ -30,6 +31,12 @@ export class KnownFileType {
         });
     }
 
+    public createFile(content: string, fileName: string): File {
+        return new File([content], this.formatFileName(fileName), {
+            type: this.contentType,
+        });
+    }
+
     public static parse(extension: string): KnownFileType | undefined {
         return KnownFileType.allInstancesByExtension[extension];
     }