Enable JDK 21 in builds

Author: ascopes

.github/workflows/build.yml

@@ -30,6 +30,8 @@ jobs:
           #   to support Java 20 bytecode. Therefore, we have to skip coverage here.
           - os-name: ubuntu-22.04
             java-version: 20-ea
+          - os-name: ubuntu-22.04
+            java-version: 21-ea
 
           # MacOS builds (only check Java 11 and 19).
           - os-name: macos-12

README.md

@@ -1,10 +1,10 @@
-![Java 11+](https://img.shields.io/badge/Java-11+-yellow?logo=openjdk)
+![Java 11+](https://img.shields.io/badge/Java-11--21-brown?logo=openjdk)
 [![Build Status](https://github.com/ascopes/java-compiler-testing/actions/workflows/build.yml/badge.svg?branch=main)](https://github.com/ascopes/java-compiler-testing/actions/workflows/build.yml)
 [![Maven Central](https://img.shields.io/maven-central/v/io.github.ascopes.jct/java-compiler-testing)](https://repo1.maven.org/maven2/io/github/ascopes/jct/java-compiler-testing)
 [![Code Coverage](https://codecov.io/gh/ascopes/java-compiler-testing/branch/main/graph/badge.svg?token=VT74BP2742)](https://codecov.io/gh/ascopes/java-compiler-testing)
 [![javadoc (latest release)](https://javadoc.io/badge2/io.github.ascopes.jct/java-compiler-testing/javadoc.svg)](https://javadoc.io/doc/io.github.ascopes.jct/java-compiler-testing)
-[![javadoc (main branch)](https://img.shields.io/badge/javadoc-snapshot-brightgreen)](https://ascopes.github.io/java-compiler-testing)
-[![Issues](https://img.shields.io/github/issues-raw/ascopes/java-compiler-testing?color=orange)](https://github.com/ascopes/java-compiler-testing/issues)
+[![javadoc (main branch)](https://img.shields.io/badge/javadoc-snapshot-darkgreen)](https://ascopes.github.io/java-compiler-testing)
+[![Issues](https://img.shields.io/github/issues-raw/ascopes/java-compiler-testing?color=red)](https://github.com/ascopes/java-compiler-testing/issues)
 [![License](https://img.shields.io/github/license/ascopes/java-compiler-testing?color=blueviolet)](https://github.com/ascopes/java-compiler-testing/blob/main/LICENSE.txt)
 ![Activity](https://img.shields.io/github/commit-activity/y/ascopes/java-compiler-testing)