ci: Add web build task for web.tgz

Jenkinsfile

@@ -44,5 +44,33 @@ pipeline {
                 }
             }
         }
+
+        stage("Build Web App") {
+            agent {
+                label 'linux'
+            }
+
+            steps {
+                script {
+                    sh '''
+                    #!/bin/bash
+
+                    flutter build web
+
+                    cd build/web
+                    tar -cvf ../../web.tgz .
+                    cd ../..
+                    '''
+                }
+            }
+
+            post {
+                always {
+                    archiveArtifacts artifacts: "web.tgz"
+
+                    cleanWs()
+                }
+            }
+        }
     }
 }