packer: add packer to tldr (#3888)

pages/common/packer.md

@@ -0,0 +1,12 @@
+# packer
+
+> Build automated machine images.
+> More information: <https://www.packer.io/>.
+
+- Build an image:
+
+`packer build {{path/to/config.json}}`
+
+- Check the syntax of a Packer image config:
+
+`packer validate {{path/to/config.json}}`