lint: Enforce camelCase

All variables should be in camelCase, so configure the corresponding
rule to enforce this. Exempt properties for now, to accommodate the
existing practice of using C-style underscore names for construct
properties of introspected objects.

https://gitlab.gnome.org/GNOME/gnome-shell-extensions/merge_requests/50

lint/eslintrc-shell.json

@@ -1,6 +1,13 @@
 {
     "rules": {
         "arrow-spacing": "error",
+        "camelcase": [
+            "error",
+            {
+                "properties": "never",
+                "allow": ["^vfunc_"]
+            }
+        ],
         "object-curly-spacing": [
             "error",
             "always"