fix(classes.dockerfile): use a single top-level fs import instead of requiring fs inside methods

ts/classes.dockerfile.ts

@@ -4,6 +4,7 @@ import { logger } from './tsdocker.logging.js';
 import { DockerRegistry } from './classes.dockerregistry.js';
 import type { IDockerfileOptions, ITsDockerConfig } from './interfaces/index.js';
 import type { TsDockerManager } from './classes.tsdockermanager.js';
+import * as fs from 'fs';
 
 const smartshellInstance = new plugins.smartshell.Smartshell({
   executor: 'bash',
@@ -314,7 +315,6 @@ export class Dockerfile {
     this.containerName = 'dockerfile-' + this.version;
 
     if (options.filePath && options.read) {
-      const fs = require('fs');
       this.content = fs.readFileSync(plugins.path.resolve(options.filePath), 'utf-8');
     } else if (options.fileContents) {
       this.content = options.fileContents;
@@ -419,7 +419,6 @@ export class Dockerfile {
     const testDir = this.managerRef.config.testDir || plugins.path.join(paths.cwd, 'test');
     const testFile = plugins.path.join(testDir, 'test_' + this.version + '.sh');
 
-    const fs = require('fs');
     const testFileExists = fs.existsSync(testFile);
 
     if (testFileExists) {