Update README

Author: sungshik

README.md

@@ -1,5 +1,7 @@
 # rascal-textmate
 
+## Background
+
 The aim of this project is to design and implement a scalable converter from
 Rascal grammars to TextMate grammars. TextMate grammars generated in this way
 are intended to be included in VS Code extensions to provide syntax highlighting
@@ -16,12 +18,56 @@ TextMate grammars, this project applies partial conversion. Alternatively, a
 previous [project](https://github.com/TarVK/syntax-highlighter) by
 [@TarVK](https://github.com/TarVK) applies total conversion.
 
-## Documentation
+## Usage
+
+### Installing `rascal-textmate`
+
+Enter the following commands in a terminal:
+
+```
+git clone https://github.com/SWAT-engineering/rascal-textmate.git
+cd rascal-textmate/rascal-textmate-core
+mvn install -Drascal.compile.skip -Drascal.tutor.skip -DskipTests
+cd ../..
+rm -rf rascal-textmate
+```
+
+### Running `rascal-textmate` in an existing Rascal project
+
+ 1. Add the following dependency in `pom.xml` of the project:
+
+    ```
+    <dependency>
+      <groupId>org.rascalmpl</groupId>
+      <artifactId>rascal-textmate-core</artifactId>
+      <version>0.1.0-SNAPSHOT</version>
+    </dependency>
+    ```
+
+ 2. Add `|lib://rascal-textmate-core|` to `Require-Libraries` in
+    `META-INF/RASCAL.MF` of the project.
+
+ 3. Open a REPL in a grammar module of the project, import module
+    `lang::textmate::main::Main` in the REPL, and run function
+    [`main`](https://github.com/SWAT-engineering/rascal-textmate/blob/69bd92c1e39b51c78ad6d49e680bba212a8df2a7/rascal-textmate-core/src/main/rascal/Main.rsc#L38-L47)
+    on the start symbol of the grammar. For instance:
+
+    ```
+    main(#Foo, "source.foo", |home:///Desktop/foo.json|)
+    ```
+
+    The generated TextMate grammar (as a JSON file) can now be integrated in a
+    VS Code extension as explained
+    [here](https://code.visualstudio.com/api/language-extensions/syntax-highlight-guide#contributing-a-basic-grammar).
+
+## Contributing
+
+### Documentation
 
 The [walkthrough](rascal-textmate-core/src/main/rascal/lang/textmate/conversiontests/Walkthrough.rsc)
-explains the main ideas behind the conversion algorithm in this project.
+explains the main ideas behind the conversion algorithm.
 
-## Tests
+### Tests
 
 To test tokenization (as part of the conversion
 [tests](rascal-textmate-core/src/main/rascal/lang/textmate/conversiontests)),