Update: support "bigint" in valid-typeof rule (#11802)

* Update: support "bigint" in valid-typeof rule

BigInt just moved to Stage 4, so add support for it to
the valid-typeof rule.

* Docs: add Further Reading to valid-typeof rule

This commit adds a Further Reading section to the
valid-typeof rule documentation.

docs/rules/valid-typeof.md

@@ -1,6 +1,6 @@
 # enforce comparing `typeof` expressions against valid strings (valid-typeof)
 
-For a vast majority of use cases, the result of the `typeof` operator is one of the following string literals: `"undefined"`, `"object"`, `"boolean"`, `"number"`, `"string"`, `"function"` and `"symbol"`. It is usually a typing mistake to compare the result of a `typeof` operator to other string literals.
+For a vast majority of use cases, the result of the `typeof` operator is one of the following string literals: `"undefined"`, `"object"`, `"boolean"`, `"number"`, `"string"`, `"function"`, `"symbol"`, and `"bigint"`. It is usually a typing mistake to compare the result of a `typeof` operator to other string literals.
 
 ## Rule Details
 
@@ -57,3 +57,7 @@ typeof bar === typeof qux
 ## When Not To Use It
 
 You may want to turn this rule off if you will be using the `typeof` operator on host objects.
+
+## Further Reading
+
+* [MDN: `typeof` documentation](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/typeof)

lib/rules/valid-typeof.js

@@ -39,7 +39,7 @@ module.exports = {
 
     create(context) {
 
-        const VALID_TYPES = ["symbol", "undefined", "object", "boolean", "number", "string", "function"],
+        const VALID_TYPES = ["symbol", "undefined", "object", "boolean", "number", "string", "function", "bigint"],
             OPERATORS = ["==", "===", "!=", "!=="];
 
         const requireStringLiterals = context.options[0] && context.options[0].requireStringLiterals;

tests/lib/rules/valid-typeof.js

@@ -26,6 +26,7 @@ ruleTester.run("valid-typeof", rule, {
         "typeof foo === 'undefined'",
         "typeof foo === 'boolean'",
         "typeof foo === 'number'",
+        "typeof foo === 'bigint'",
         "'string' === typeof foo",
         "'object' === typeof foo",
         "'function' === typeof foo",