feat: allow custom descriptors in no-invalid-at-rules (eslint#128)

* feat: allow custom descriptors in no-invalid-at-rules

* Update src/rules/no-invalid-at-rules.js

* Update src/rules/no-invalid-at-rules.js

* Update src/rules/no-invalid-at-rules.js

---------

Co-authored-by: Nicholas C. Zakas <nicholas@humanwhocodes.com>

Author: thecalamiity

src/rules/no-invalid-at-rules.js

@@ -121,6 +121,11 @@ export default {
 			},
 
 			"AtRule > Block > Declaration"(node) {
+				// skip custom descriptors
+				if (node.property.startsWith("--")) {
+					return;
+				}
+
 				// get at rule node
 				const atRule = /** @type {AtrulePlain} */ (
 					sourceCode.getParent(sourceCode.getParent(node))

tests/rules/no-invalid-at-rules.test.js

@@ -67,6 +67,19 @@ ruleTester.run("no-invalid-at-rules", rule, {
 				customSyntax: tailwindSyntax,
 			},
 		},
+		{
+			code: `@custom-rule {
+				--foo: red;
+				--bar: blue;
+			}`,
+			languageOptions: {
+				customSyntax: {
+					atrules: {
+						"custom-rule": {},
+					},
+				},
+			},
+		},
 	],
 	invalid: [
 		{