Revert "Removes outdated file for CFE"

Why don't we love CrossFeedEnabler anymore? I don't understand.

This reverts commit 064d00b7be.

CrossFeedEnabler-v3.1.ckan

@@ -0,0 +1,16 @@
+{
+  "spec_version": 1,
+  "identifier": "CrossFeedEnabler",
+  "name": "Crossfeed Enabler",
+  "abstract": "Adds toggleable fuel crossfeed between the part it's added to, and the part this part is surface-attached to. Use it for radial tanks.",
+  "license": "CC-BY-SA",
+  "ksp_version": "0.25",
+  "resources": {
+    "repository": "https://github.com/NathanKell/CrossFeedEnabler"
+  },
+  "author": "NathanKell",
+  "version": "v3.1",
+  "download": "https://github.com/NathanKell/CrossFeedEnabler/releases/download/v3.1/CrossFeedEnabler_v3.1.zip",
+  "x_generated_by": "netkan",
+  "download_size": 30773
+}