Other: Add whitespace rules from GJS Style Guide and fix complaints

Add whitespace rules from GJS Style Guide to ESLint config and fix new
complaints.
See here for the GJS Style guide whitespace section:
https://gjs.guide/guides/gjs/style-guide.html#whitespace

.eslintrc.yml

@@ -20,6 +20,28 @@ rules:
   no-unused-vars:
     - error
     - argsIgnorePattern: "^_"
+  # Rules from GJS Style Guide regarding whitespace.
+  # See here: https://gjs.guide/guides/gjs/style-guide.html#whitespace
+  func-call-spacing:
+    - error
+    - never
+  array-bracket-spacing:
+    - error
+    - never
+  space-before-function-paren:
+    - error
+    - never
+  space-before-blocks:
+    - error
+    - always
+  key-spacing:
+    - error
+    - beforeColon: false
+      afterColon: true
+      mode: strict
+  object-curly-spacing:
+    - error
+    - always
 globals:
   imports: readonly
   log: readonly