feat(exemples-packer): Ajout template de base Ubuntu Jammy

exemples-packer/ubuntu-jammy-base.pkr.hcl

+# Pull d'une image Ubuntu 22.04 LTS
+source "docker" "ubuntu-formation-cnrs" {
+    image = "ubuntu:jammy"
+    commit = true
+}
+
+# Construire l'image "personnalisée"
+build {
+  sources = [
+    "source.docker.ubuntu-formation-cnrs"
+  ]
+
+  # Tag de l'image Docker créé
+  post-processors {
+    post-processor "docker-tag" {
+      repository =  "local/ubuntu-formation-cnrs"
+      tags = [
+        "22.04.2",
+        "latest"
+      ]
+    }
+  }
+}
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