Add README.md and link to CONTRIBUTING.md

CONTRIBUTING.md

@@ -45,6 +45,9 @@ See [Debugging](./docs/debugging.md).
 If you want to develop on the web assembly side you can run `yarn serve` and then go
 to <http://localhost:8080>.
 
+### boa-unicode
+Boa uses the library `boa-unicode` to query Unicode character properties and classes in lexer and parser. See [boa_unicode/README.md](./boa_unicode/README.md) for development and more information.
+
 ### Setup
 
 #### VSCode Plugins

boa_unicode/README.md

@@ -0,0 +1,21 @@
+# boa-unicode
+
+`boa-unicode` defines the trait to provide methods for querying properties or classes for Unicode identifiers. These properties are used to determine if a code point (char) is valid for being the start/part of an identifier in lexer and parser.
+
+Current version: Unicode 13.0.0
+
+## Development
+The Unicode character tables used to query properties are generated by `build_tables.js`. This script depends on [Node.js](https://nodejs.org/en/) and [rustfmt](https://github.com/rust-lang/rustfmt). You can run the script with:
+```
+$ node build_tables.js
+```
+or with [npm](https://www.npmjs.com/):
+```
+$ npm run build-tables
+```
+
+The configurations are defined as constants in the script. Please check the comments in `build_tables.js` for more information.
+
+## More Info
+- [Unicode® Standard Annex #31 - UNICODE IDENTIFIER AND PATTERN SYNTAX](https://unicode.org/reports/tr31/)
+- [Unicode® Standard Annex #44 - UNICODE CHARACTER DATABASE](https://unicode.org/reports/tr44/)

boa_unicode/src/lib.rs

@@ -1,4 +1,4 @@
-//! This crate implements the extension to query if a char belongs to a particular unicode identifier property.
+//! This library implements the extension to query if a char belongs to a particular unicode identifier property.
 //! Version: Unicode 13.0.0
 //!
 //! More information: