Prepare version 4: use Markdown in Release Notes, move non-release information to README.

Author: carlosame

README.md

@@ -14,6 +14,15 @@ This software is provided under a [BSD-style license](LICENSE.txt).
 
 <br/>
 
+## Java™ Runtime Environment requirements
+
+All the classes in the binary package have been compiled with a [Java compiler](https://adoptium.net/)
+set to 1.8 compiler compliance level, except the `module-info.java` file.
+
+Building this library requires JDK 11 or higher.
+
+<br/>
+
 ## Building from source
 
 ### Requirements
@@ -58,3 +67,30 @@ Before deploying to a remote Maven repository, please read the
 to learn which properties you need to set (like `mavenReleaseRepoUrl`or
 `mavenRepoUsername`), either at the [command line](https://docs.gradle.org/current/userguide/build_environment.html#sec:project_properties)
 (`-P` option) or your `GRADLE_USER_HOME/gradle.properties` file.
+
+<br/>
+
+## Software dependencies
+
+In case that you do not use a Gradle or Maven build (which would manage the
+dependencies according to the relevant `.module` or `.pom` files), the required
+and optional library packages are the following:
+
+### Compile-time dependencies
+
+- The [carte-util](https://github.com/css4j/carte-util) library; version 3.5.1
+  or higher is recommended.
+
+- The [jclf-text](https://jclf.sourceforge.io/api/io.sf.jclf.text/module-summary.html)
+  (5.0.0 or higher) module. See: https://sourceforge.net/projects/jclf
+
+  **It is optional at runtime.**
+
+- The [tokenproducer](https://github.com/css4j/tokenproducer) library; version
+  1.1.1 or higher is recommended.
+
+  **It is optional at runtime.**
+
+### Test dependency
+
+- A recent version of [JUnit 4](https://junit.org/junit4/).

RELEASE_NOTES.md

@@ -0,0 +1,28 @@
+# xml-dtd version 4.0.0 Release Notes
+
+### December 3, 2021
+
+<br/>
+
+## Highlights
+
+### Removal of DefaultEntityResolver.resolveEntity(String)
+
+See issue #1.
+
+### Use the Security Manager if available
+
+See issue #2.
+
+## Detail of changes
+
+- Remove `DefaultEntityResolver.resolveEntity(String)`. (#1)
+- Use the Security Manager only if available. (#2)
+- Gradle: copy licensing files to `META-INF` directory of archive files.
+- Gradle: line-ending conversion task now warns if file does not exists.
+- Gradle: upgrade wrapper to 7.3.
+- Upgrade to JUnit 4.13.2.
+- Add a 'changes.sh' script to generate a CHANGES.txt.
+- Use Markdown in Release Notes, move non-release information to README.
+- README: add a link to the resolver overview/introduction page.
+- CI: build with Java 11 and 17.

RELEASE_NOTES.txt

@@ -7,7 +7,7 @@ group = 'io.sf.carte'
 
 description = 'xml-dtd'
 
-version = '3.5.2'
+version = '4.0.0'
 
 sourceSets {
 	main {