chore(build): upgrade Java baseline to 17 (#17)

Raises sourceCompatibility and targetCompatibility from Java 8 to Java 17.
Gradle 9 already requires Java 17 to run, so Java 8 was never a realistic
consumer constraint. Updates README requirements accordingly and removes
the Credits section.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: jimisola

README.adoc

@@ -139,14 +139,11 @@ gradle assembleRequirements
 
 == Requirements
 
-* Gradle 6.0+ (tested with Gradle 9.3)
-* Java 8+
+* Gradle 9.0+
+* Java 17+
 * A `requirements.yml` file in the dataset directory (default: `./reqstool/`)
 
 == License
 
 MIT License - see link:LICENSE[LICENSE] file for details
 
-== Credits
-
-Based on link:https://github.com/Luftfartsverket/reqstool-java-maven-plugin[reqstool-java-maven-plugin] by Luftfartsverket (LFV).

build.gradle

@@ -10,8 +10,8 @@ group = 'se.lfv.reqstool'
 version = '0.1.0'
 
 java {
-    sourceCompatibility = JavaVersion.VERSION_1_8
-    targetCompatibility = JavaVersion.VERSION_1_8
+    sourceCompatibility = JavaVersion.VERSION_17
+    targetCompatibility = JavaVersion.VERSION_17
 }
 
 repositories {