✨ add es/no-object-keys rule (#21)

docs/rules/no-object-keys.md

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+# disallow the `Object.keys` method (es/no-object-keys)
+
+This rule reports ES5 `Object.keys` method as errors.
+
+## Examples
+
+⛔ Examples of **incorrect** code for this rule:
+
+<eslint-playground type="bad" code="/*eslint es/no-object-keys: error */
+const keys = Object.keys(obj)
+" />
+
+## 📚 References
+
+- [Rule source](https://github.com/mysticatea/eslint-plugin-es/blob/v2.0.0/lib/rules/no-object-keys.js)
+- [Test source](https://github.com/mysticatea/eslint-plugin-es/blob/v2.0.0/tests/lib/rules/no-object-keys.js)

lib/rules/no-object-keys.js

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+/**
+ * @author Toru Nagashima <https://github.com/mysticatea>
+ * See LICENSE file in root directory for full license.
+ */
+"use strict"
+
+const { READ, ReferenceTracker } = require("eslint-utils")
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "disallow the `Object.keys` method.",
+            category: "ES5",
+            recommended: false,
+            url:
+                "http://mysticatea.github.io/eslint-plugin-es/rules/no-object-keys.html",
+        },
+        fixable: null,
+        messages: {
+            forbidden: "ES5 '{{name}}' method is forbidden.",
+        },
+        schema: [],
+        type: "problem",
+    },
+    create(context) {
+        return {
+            "Program:exit"() {
+                const tracker = new ReferenceTracker(context.getScope())
+                for (const { node, path } of tracker.iterateGlobalReferences({
+                    Object: {
+                        keys: { [READ]: true },
+                    },
+                })) {
+                    context.report({
+                        node,
+                        messageId: "forbidden",
+                        data: { name: path.join(".") },
+                    })
+                }
+            },
+        }
+    },
+}

tests/lib/rules/no-object-keys.js

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+/**
+ * @author Toru Nagashima <https://github.com/mysticatea>
+ * See LICENSE file in root directory for full license.
+ */
+"use strict"
+
+const RuleTester = require("../../tester")
+const rule = require("../../../lib/rules/no-object-keys.js")
+
+new RuleTester().run("no-object-keys", rule, {
+    valid: ["Object", "Object.assign", "let Object = 0; Object.keys"],
+    invalid: [
+        {
+            code: "Object.keys",
+            errors: ["ES5 'Object.keys' method is forbidden."],
+        },
+    ],
+})