Merge #795: docs: added icons for stars, contributors, forks, issues and links to them

9338f7d Update README.md (Ocheretovich)

Pull request description:

ACKs for top commit:
  apoelstra:
    ACK 9338f7d; successfully ran local tests

Tree-SHA512: 79eb4888f26a1668963e46630d2c4d28d2f2adaf89920e2b522f5387119eb624114d258dd7047503a3f01ccbfbf9668af3d9b99ce4876ae191c3b5b33741da68

Author: apoelstra

README.md

@@ -1,4 +1,8 @@
+[![Stars](https://img.shields.io/github/stars/rust-bitcoin/rust-miniscript)](https://github.com/rust-bitcoin/rust-miniscript/stargazers)
+[![Forks](https://img.shields.io/github/forks/rust-bitcoin/rust-miniscript)](https://github.com/rust-bitcoin/rust-miniscript/network/members)
+[![Contributors](https://img.shields.io/github/contributors/rust-bitcoin/rust-miniscript)](https://github.com/rust-bitcoin/rust-miniscript/graphs/contributors)
 [![Build](https://github.com/rust-bitcoin/rust-miniscript/workflows/Continuous%20integration/badge.svg)](https://github.com/rust-bitcoin/rust-miniscript/actions)
+[![Issues](https://img.shields.io/github/issues-raw/rust-bitcoin/rust-miniscript)](https://github.com/rust-bitcoin/rust-miniscript/issues)
 
 **Minimum Supported Rust Version:** 1.63.0