Switch from Travis CI to GitHub Actions for CI pipeline.

Replaced the deprecated Travis CI configuration with a GitHub Actions workflow. Updated the build status badge in the README to reflect the new CI provider. This transition modernizes the CI setup and ensures future maintainability.

Author: anlun

.github/workflows/main.yml

@@ -0,0 +1,29 @@
+name: CI
+
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+    branches: [ main, master ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    
+    - name: Set up JDK 11
+      uses: actions/setup-java@v2
+      with:
+        java-version: '11'
+        distribution: 'adopt'
+        
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+      
+    - name: Build with Gradle
+      run: ./gradlew build
+      
+    - name: Run tests
+      run: ./gradlew test

.travis.yml

@@ -1,7 +1,7 @@
-# parserCombinators [![Build Status](https://travis-ci.org/anlun/parserCombinators.svg?branch=master)](https://travis-ci.org/anlun/parserCombinators)
+# parserCombinators ![GitHub CI](https://github.com/anlun/parserCombinators/workflows/CI/badge.svg)
+
+The parser combinator library written in Kotlin.  
 
-The parser combinator library written on Kotlin.  
-  
 # Build instruction:
 
 * Install [Gradle](https://gradle.org)