Merge branch 'release-v4.0'

CHANGELOG.md

 # Changelog
 
-## Unreleased
+## 4.0.0 (2021-03-23)
 
  * `IERC20Metadata`: add a new extended interface that includes the optional `name()`, `symbol()` and `decimals()` functions. ([#2561](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2561))
  * `ERC777`: make reception acquirement optional in `_mint`. ([#2552](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2552))
@@ -31,7 +31,6 @@
 
  * `AccessControlEnumerable`: Fixed `renounceRole` not updating enumerable set of addresses for a role. ([#2572](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2572))
 
-
 ### How to upgrade from 3.x
 
 Since this version has moved a few contracts to different directories, users upgrading from a previous version will need to adjust their import statements. To make this easier, the package includes a script that will migrate import statements automatically. After upgrading to the latest version of the package, run:

contracts/package.json

 {
   "name": "@openzeppelin/contracts",
   "description": "Secure Smart Contract library for Solidity",
-  "version": "3.4.0",
+  "version": "4.0.0",
   "files": [
     "**/*.sol",
     "/build/contracts/*.json",

docs/antora.yml

 name: contracts
 title: Contracts
-version: 3.x
+version: 4.x
 nav:
   - modules/ROOT/nav.adoc
   - modules/api/nav.adoc

package.json

 {
   "name": "openzeppelin-solidity",
   "description": "Secure Smart Contract library for Solidity",
-  "version": "3.4.0",
+  "version": "4.0.0",
   "files": [
     "/contracts/**/*.sol",
     "/build/contracts/*.json",