lint: Tweak the whitelist of globals

gjs doesn't include any gettext wrappers, and obviously can't know
about the shell's global object, so include those in the list of
globals for all sources in the gnome-shell context.

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

.eslintrc.json

@@ -1,5 +1,6 @@
 {
     "extends": [
-        "./lint/eslintrc-gjs.json"
+        "./lint/eslintrc-gjs.json",
+        "./lint/eslintrc-shell.json"
     ]
 }

lint/eslintrc-shell.json

@@ -0,0 +1,15 @@
+{
+    "overrides": [
+        {
+            "files": "js/**",
+            "excludedFiles": ["js/extensionPrefs/*", "js/portalHelper/*"],
+            "globals": {
+                "global": false,
+                "_": false,
+                "C_": false,
+                "N_": false,
+                "ngettext": false
+            }
+        }
+    ]
+}