Define basic GitHub Actions build (#56)

Author: pivovarit

.github/workflows/build.yml

@@ -0,0 +1,29 @@
+name: build
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        java: [ '8' ]
+        architecture: [ 'x64' ]
+    name: Build with JDK ${{ matrix.java }} on ${{ matrix.architecture }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Setup JDK
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: ${{ matrix.java }}
+          architecture: ${{ matrix.architecture }}
+          cache: 'gradle'
+
+      - name: Build with Gradle
+        run: ./gradlew asciidoc

README.adoc

@@ -2,14 +2,10 @@
 
 This is the source of the http://docs.vavr.io/[Vavr documentation].
 
-=== Performing Updates
+== Performing Updates
 
-* Ensure `~/.gradle/gradle.properties` exists with:
-
-  githubUser=<GitHub user>
-  githubPassword=<GitHub password>
+* Ensure that `GITHUB_USER` and `GITHUB_TOKEN` variables are set in your environment.
 
 * Update the version in `gradle.properties`. Please note that the version in the Maven section of `getting_started.adoc` currently has to be updated manually.
 * Write documentation and test results with `./gradlew asciidoc`. If the Vavr API has changed, some code example tests might fail.
 * Then `git commit`, `git push` and `./gradlew publishGhPages`
-* Nowadays, `githubPassword` effectively means a token and not the actual password!

build.gradle

@@ -94,8 +94,8 @@ githubPages {
     repoUri = 'https://github.com/vavr-io/vavr-docs.git'
 
     credentials {
-        username = project.githubUser
-        password = project.githubPassword
+        username = System.getenv('GITHUB_USER') ?: ''
+        password = System.getenv('GITHUB_TOKEN') ?: ''
     }
 
     pages {