Update MSRV in readme

Update the documented MSRV as well as the badges.

Author: chain-forgexcr45

README.md

@@ -6,7 +6,7 @@
     <a href="https://github.com/rust-bitcoin/rust-secp256k1/blob/master/LICENSE"><img alt="CC0 1.0 Universal Licensed" src="https://img.shields.io/badge/license-CC0--1.0-blue.svg"/></a>
     <a href="https://github.com/rust-bitcoin/rust-secp256k1/actions?query=workflow%3AContinuous%20integration"><img alt="CI Status" src="https://github.com/rust-bitcoin/rust-secp256k1/workflows/Continuous%20integration/badge.svg"></a>
     <a href="https://docs.rs/secp256k1"><img alt="API Docs" src="https://img.shields.io/badge/docs.rs-secp256k1-green"/></a>
-    <a href="https://blog.rust-lang.org/2020/02/27/Rust-1.56.1.html"><img alt="Rustc Version 1.56.1+" src="https://img.shields.io/badge/rustc-1.56.1.0%2B-lightgrey.svg"/></a>
+    <a href="https://blog.rust-lang.org/2020/02/27/Rust-1.63.0.html"><img alt="Rustc Version 1.63.0+" src="https://img.shields.io/badge/rustc-1.63.0.0%2B-lightgrey.svg"/></a>
   </p>
 </div>
 
@@ -29,7 +29,7 @@ Contributions to this library are welcome. A few guidelines:
 * Any breaking changes must have an accompanied entry in CHANGELOG.md
 * No new dependencies, please.
 * No crypto should be implemented in Rust, with the possible exception of hash functions. Cryptographic contributions should be directed upstream to libsecp256k1.
-* This library should always compile with any combination of features on **Rust 1.56.1**.
+* This library should always compile with any combination of features on **Rust 1.63.0**.
 
 ### Githooks