Fix file writes to non-existent directories

When the game attempts to create the settings file but its directory
does not exist yet, an early error occurs. In reality, there is no way
for the directory to be created without user intervention. This change
makes sure the directory is created before any attempt to write a file
is done. Errors related to directory creation and/or file writes are
still reported as usual.

electron/src/fsjob.ts

@@ -49,6 +49,10 @@ export class FsJobHandler {
     }
 
     private async write(file: string, contents: string): Promise<string> {
+        // The target directory might not exist, ensure it does
+        const parentDir = path.dirname(file);
+        await fs.mkdir(parentDir, { recursive: true });
+
         // Backups not implemented yet.
         await fs.writeFile(file, contents, {
             encoding: "utf-8",