.eslintrc.json: use jsonc/no-irregular-whitespace

The eslint-plugin-jsonc documentation recommends turning ESLint's
own no-irregular-whitespace plugin off for JSON files in favor of
its own jsonc/no-irregular-whitespace plugin.

The idea here is to allow "irregular" whitespace in quoted strings
and regular expressions, as that may be deliberate, and to forbid
such whitespace in comments and templates (though I'm unsure if we
should skip them in templates?).

See: https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-irregular-whitespace.html

.eslintrc.json

@@ -272,7 +272,17 @@
         "plugin:jsonc/recommended-with-json5"
       ],
       "rules": {
-        "no-irregular-whitespace": "error",
+        // ESLint core no-irregular-whitespace rule doesn't work well in JSON
+        "no-irregular-whitespace": "off",
+        "jsonc/no-irregular-whitespace": [
+          "error",
+          {
+            "skipStrings": true,
+            "skipComments": false,
+            "skipRegExps": true,
+            "skipTemplates": false
+          }
+        ],
         "no-trailing-spaces": "error",
         "jsonc/comma-dangle": [
           "error",