Merge pull request #23 from sc0Vu/update-2020-links

fix: links in ES2020.MD

Author: daumann

ES2020.MD

@@ -9,8 +9,8 @@ ES2020 includes the following new feature proposals:
 
 - [Dynamic Imports](#dynamic-imports)
 - [`BigInt`](#bigint)
-- [Nullish Coalescing Operator](#nullish-coalescing-operator)
-- [Optional Chaining Operator](#optional-chaining-operator)
+- [Nullish Coalescing Operator](#nullish-coalescing-operator-)
+- [Optional Chaining Operator](#optional-chaining-operator-)
 - [`Promise.allSettled()`](#promiseallsettled)
 - [`String.matchAll()`](#stringmatchall)
 - [`globalThis`](#globalthis)