lint: Allow multiple spaces before key values

This is useful for imitating namespaced flags/enums:

```
const FooFlags = {
    NONE:    0,
    SMEAGLY: 1 << 0,
    SMOGLEY: 1 << 1,
    MUGGLY:  1 << 2
};
```

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/609

lint/eslintrc-shell.json

@@ -7,6 +7,14 @@
                 "allow": ["^vfunc_", "^on_"]
             }
         ],
+        "key-spacing": [
+            "error",
+            {
+                "mode": "minimum",
+                "beforeColon": false,
+                "afterColon": true
+            }
+        ],
         "object-curly-spacing": [
             "error",
             "always"