ci: Import ci pipeline from original repo

When this repository was split from the original *dustin/sshca*
repository, the CI pipeline was not imported.  It wouldn't have mattered
if it had been, since it wouldn't have worked, anyway, given the path
changes.

ci/Jenkinsfile

@@ -0,0 +1,48 @@
+pipeline {
+    agent none
+
+    stages {
+        stage('SSHCA') {
+            stages {
+                stage('Server') {
+                    agent {
+                        kubernetes {
+                            yamlFile 'ci/podTemplate.yaml'
+                            yamlMergeStrategy merge()
+                            defaultContainer 'buildah'
+                        }
+                    }
+                    stages {
+                        stage('Build') {
+                            steps {
+                                sh '. ci/build.sh'
+                            }
+                        }
+
+                        stage('Publish') {
+                            steps {
+                                withEnv([
+                                    "REGISTRY_AUTH_FILE=${env.WORKSPACE_TMP}/auth.json"
+                                ]) {
+                                    withCredentials([usernamePassword(
+                                        credentialsId: 'jenkins-packages',
+                                        usernameVariable: 'BUILDAH_USERNAME',
+                                        passwordVariable: 'BUILDAH_PASSWORD',
+                                    )]) {
+                                        sh """
+                                            buildah login \
+                                            --username \${BUILDAH_USERNAME} \
+                                            --password \${BUILDAH_PASSWORD} \
+                                            git.pyrocufflink.net
+                                        """
+                                    }
+                                    sh '. ci/publish.sh'
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}