docs: add Ankr to list of Providers (ethers-io#2779).

Author: ricmoo

README.md

@@ -12,7 +12,7 @@ A complete Ethereum wallet implementation and utilities in JavaScript (and TypeS
 - Import and export **JSON wallets** (Geth, Parity and crowdsale)
 - Import and export BIP 39 **mnemonic phrases** (12 word backup phrases) and **HD Wallets** (English as well as Czech, French, Italian, Japanese, Korean, Simplified Chinese, Spanish, Traditional Chinese)
 - Meta-classes create JavaScript objects from any contract ABI, including **ABIv2** and **Human-Readable ABI**
-- Connect to Ethereum nodes over [JSON-RPC](https://github.com/ethereum/wiki/wiki/JSON-RPC), [INFURA](https://infura.io), [Etherscan](https://etherscan.io), [Alchemy](https://alchemyapi.io) or [MetaMask](https://metamask.io)
+- Connect to Ethereum nodes over [JSON-RPC](https://github.com/ethereum/wiki/wiki/JSON-RPC), [INFURA](https://infura.io), [Etherscan](https://etherscan.io), [Alchemy](https://alchemyapi.io), [Ankr](https://ankr.com) or [MetaMask](https://metamask.io)
 - **ENS names** are first-class citizens; they can be used anywhere an Ethereum addresses can be used
 - **Tiny** (~104kb compressed; 322kb uncompressed)
 - **Modular** packages; include only what you need