docs: ✏️ add README

README.md

@@ -1,3 +1,64 @@
 # GumTree
 
-The implementation of GumTree algorithm in Kotlin.
+[![codecov](https://codecov.io/github/Xanonymous-GitHub/gumtree/graph/badge.svg?token=APHSDWWVC4)](https://codecov.io/github/Xanonymous-GitHub/gumtree)
+
+**Description:**
+
+GumTree is a Kotlin library for implementing the GumTree algorithm.
+
+The origin paper can be found at [here](https://doi.org/10.1145/2642937.2642982)
+
+**Getting Started**
+
+1. **Prerequisites:**
+    * **JDK:** Gumtree requires JDK 21 to build and run. 
+
+2. **Clone the Repository:**
+   ```bash
+   git clone [email protected]:Xanonymous-GitHub/gumtree.git
+   ```
+
+3. **Build the Project:**
+   ```bash
+   ./gradlew build
+   ```
+
+> [!NOTE]
+> This also runs the tests.
+
+4. **Run Unit Tests:**
+   ```bash
+   ./gradlew test
+   ```
+
+> [!TIP]
+> Human-readable unit tests report generated by Kover can be found in `build/reports/kover/html/index.html`.
+> The build folder is generated in each Gradle subproject after running the `test` task.
+
+**Usages**
+
+This project currently supports converting ANTLR's parse tree to `GumTree`.
+Assume we have a file, and `UrlLexer` and `UrlParser` are the lexer and parser for URLs.
+Then we can convert the file to a `GumTree` as follows:
+
+```kotlin
+// This API is defined in the `antlr-bridge` module.
+
+val file = File("src/test/kotlin/data/urls.txt")
+val inputStream = file.inputStream()
+runBlocking {
+    GumTreeConverter.convertFrom(inputStream, ::UrlLexer, ::UrlParser, UrlParser::url)
+}
+```
+
+You can use the `DiffCalculator` class to compute the edit script between two `GumTree`s.
+
+```kotlin
+val (tree1, tree2) = treePair
+val calculator = DiffCalculator()
+
+runBlocking {
+    val editScript = calculator.computeEditScriptFrom(tree1 to tree2)
+    assertEquals(7, editScript.size)
+}
+```