Add Dockerfile support for Jenkins

Jenkinsfile

@@ -1,5 +1,7 @@
 pipeline {
-agent any 
+agent {
+        dockerfile true
+    } 
 parameters {
     string(defaultValue: '5', description: 'Amount of lines to cut off the file.', name: 'CUTOFF', trim: false)
 }
@@ -8,6 +10,7 @@ stages {
            steps { 
             withEnv(["KAGGLE_USERNAME=${params.KAGGLE_USERNAME}",
             "KAGGLE_KEY=${params.KAGGLE_KEY}", "CUTOFF=${params.CUTOFF}" ]) {
+                sh 'python3 script.py'
                 // Uruchomienie skryptu
                 sh "chmod 777 ./data_download.sh"
                 sh "./data_download.sh"