chore: add badges to per-crate READMEs

rsjsonnet-front/README.md

@@ -1,4 +1,9 @@
 # rsjsonnet-front
 
+[![crates.io](https://img.shields.io/crates/v/rsjsonnet-front.svg)](https://crates.io/crates/rsjsonnet-front)
+[![Documentation](https://docs.rs/rsjsonnet-front/badge.svg)](https://docs.rs/rsjsonnet-front)
+![MSRV](https://img.shields.io/badge/rustc-1.74+-lightgray.svg)
+[![License](https://img.shields.io/crates/l/rsjsonnet-front.svg)](https://github.com/eduardosm/rsjsonnet#license)
+
 A Rust library that sits in the middle between rsjsonnet-lang and
 the outer world. Provides source loading and error printing.

rsjsonnet-lang/README.md

@@ -1,4 +1,9 @@
 # rsjsonnet-lang
 
+[![crates.io](https://img.shields.io/crates/v/rsjsonnet-lang.svg)](https://crates.io/crates/rsjsonnet-lang)
+[![Documentation](https://docs.rs/rsjsonnet-lang/badge.svg)](https://docs.rs/rsjsonnet-lang)
+![MSRV](https://img.shields.io/badge/rustc-1.74+-lightgray.svg)
+[![License](https://img.shields.io/crates/l/rsjsonnet-lang.svg)](https://github.com/eduardosm/rsjsonnet#license)
+
 A Rust library to parse and evaluate [Jsonnet](https://jsonnet.org/)
 programs.

rsjsonnet/README.md

@@ -1,4 +1,8 @@
 # rsjsonnet
 
+[![crates.io](https://img.shields.io/crates/v/rsjsonnet.svg)](https://crates.io/crates/rsjsonnet)
+![MSRV](https://img.shields.io/badge/rustc-1.74+-lightgray.svg)
+[![License](https://img.shields.io/crates/l/rsjsonnet.svg)](https://github.com/eduardosm/rsjsonnet#license)
+
 A command line [Jsonnet](https://jsonnet.org/) interpreter implement in Rust.
 It offers an interface similar to the official implementation.