Port the index from APT to Markdown with the following changes:

* Remove the sentence saying that Java 8 is the default version. Version 4 of the plugin does not set a default version anymore.

Author: desruisseaux

src/site/apt/index.apt.vm

@@ -0,0 +1,68 @@
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+The Compiler Plugin is used to compile the sources of your project.
+The default compiler used to compile Java sources is `javac`.
+If you want to use another compiler, refer to the [using Non-Javac Compilers](/non-javac-compilers.html) page.
+
+**NOTE:** To know more about the JDK `javac`, please see the
+[tool guide](https://docs.oracle.com/en/java/javase/24/docs/specs/man/javac.html).
+
+# Goals Overview
+
+The Compiler Plugin has two goals.
+Both are already bound to their proper phases within the Maven Lifecycle and are therefore,
+automatically executed during their respective phases.
+
+* [compiler:compile](./compile-mojo.html) is bound to the compile phase and is used to compile the main source files.
+* [compiler:testCompile](./testCompile-mojo.html) is bound to the test-compile phase and is used to compile the test source files.
+
+# Usage
+
+General instructions on how to use the Compiler Plugin can be found on the [usage page](./usage.html).
+Some more specific use cases are described in the examples given below.
+
+In case you still have questions regarding the plugin's usage, please have a look at the [FAQ](./faq.html)
+and feel free to contact the [user mailing list](./mailing-lists.html).
+The posts to the mailing list are archived and could already contain the answer to your question as part of an older thread.
+Hence, it is also worth browsing/searching the [mail archive](./mailing-lists.html).
+
+If you feel the plugin is missing a feature or has a defect,
+you can file a feature request or bug report in our [issue tracker](./issue-management.html).
+When creating a new issue, please provide a comprehensive description of your concern.
+Especially for fixing bugs it is crucial that the developers can reproduce your problem.
+For this reason, entire debug logs, POMs or most preferably little demo projects attached to the issue are very much appreciated.
+Of course, patches are welcome, too.
+Contributors can check out the project from our [source repository](./scm.html) and will find supplementary information
+in the [guide to helping with Maven](http://maven.apache.org/guides/development/guide-helping.html).
+
+# Examples
+
+To provide you with better understanding on some usages of the Compiler Plugin,
+you can take a look into the following examples:
+
+* [Annotation processors](./examples/annotation-processor.html)
+* [Arguments related to Java Platform Module System](./examples/jpms_args.html)
+* [Compile using a different JDK](./examples/compile-using-different-jdk.html)
+* [Compile using a non-javac compilers](./examples/non-javac-compilers.html)
+* [Compile using the --source and --target javac options](./examples/set-compiler-source-and-target.html)
+* [Compile using the --release javac option](./examples/set-compiler-release.html)
+* [Compile using memory allocation enhancements](./examples/compile-with-memory-enhancements.html)
+* [Java 9+ projects with module-info](./examples/module-info.html)
+* [Pass compiler arguments](./examples/pass-compiler-arguments.html)