docs: add `package-info.java` and `readme.md`

For external code:
- acearth,
- zxing,
- jcckit,
- ditaa.

src/ext/plantuml/com/ctreber/acearth/package-info.java

@@ -0,0 +1,16 @@
+/*
+ * ⚠ Disclaimer 🚩
+ * This file was not part of the original package.
+ * It was included only on the PlantUML package 
+ * to provide source citation and documentation.
+ *
+ */
+/**
+ * Internal copy of <code>AC.earth</code> - <code>XEarth</code> 
+ * for Java <i>(code of Christian Treber)</i>.
+ * 
+ * @see ext.plantuml.com.ctreber.acearth.ACearth
+ * @see net.sourceforge.plantuml.acearth
+ * 
+ */
+package ext.plantuml.com.ctreber.acearth;

src/ext/plantuml/com/ctreber/acearth/readme.md

@@ -0,0 +1,12 @@
+> [!WARNING] 
+> **Disclaimer**:
+> This file was not part of the original package.
+> It was included only on the PlantUML package to provide source citation and documentation.
+
+# Directory Documentation for `acearth`
+
+## Description
+Internal copy of `AC.earth` - `XEarth` for Java _(code of Christian Treber)_.
+
+## See more information on
+- [readme of `plantuml/acearth`](../../../../../net/sourceforge/plantuml/acearth/readme.md)

src/ext/plantuml/com/google/zxing/package-info.java

@@ -0,0 +1,16 @@
+/*
+ * ⚠ Disclaimer 🚩
+ * This file was not part of the original package.
+ * It was included only on the PlantUML package 
+ * to provide source citation and documentation.
+ *
+ */
+/**
+ * Internal copy of 
+ * <a href="https://github.com/zxing/zxing" target="_top">
+ * <code>ZXing</code></a> <i>(code of Google)</i>.
+ * 
+ * @see net.sourceforge.plantuml.flashcode
+ * 
+ */
+package ext.plantuml.com.google.zxing;

src/ext/plantuml/com/google/zxing/readme.md

@@ -0,0 +1,15 @@
+> [!WARNING] 
+> **Disclaimer**:
+> This file was not part of the original package.
+> It was included only on the PlantUML package to provide source citation and documentation.
+
+# Directory Documentation for `zxing`
+
+## Description
+Internal copy of `ZXing` _(code of Google)_.
+
+## Credit
+- :octocat: [zxing/zxing](https://github.com/zxing/zxing)
+
+## See more information on
+- [readme of `plantuml/flashcode`](../../../../../net/sourceforge/plantuml/flashcode/readme.md)

src/h/package-info.java

@@ -12,9 +12,9 @@
  * </ul>
  * </p>
  * 
- * @see gen
+ * @see "gen"
  * @see gen.annotation
- * @see gen.lib
+ * @see "gen.lib"
  * @see gen.plugin.dot_layout
  * @see smetana.core
  * @see net.sourceforge.plantuml.sdot

src/jcckit/package-info.java

@@ -0,0 +1,16 @@
+/*
+ * ⚠ Disclaimer 🚩
+ * This file was not part of the original package.
+ * It was included only on the PlantUML package 
+ * to provide source citation and documentation.
+ *
+ */
+/**
+ * Internal copy of 
+ * <a href="https://jcckit.sourceforge.net" target="_top">
+ * <code>JCCKit</code></a> <i>(code of Franz-Josef Elmer)</i>.
+ * 
+ * @see net.sourceforge.plantuml.jcckit
+ * 
+ */
+package jcckit;

src/jcckit/readme.md

@@ -0,0 +1,15 @@
+> [!WARNING] 
+> **Disclaimer**:
+> This file was not part of the original package.
+> It was included only on the PlantUML package to provide source citation and documentation.
+
+# Directory Documentation for `jcckit`
+
+## Description
+Internal copy of `JCCKit` _(code of Franz-Josef Elmer)_.
+
+## Credit
+- [JCCKit _(on Sourceforge)_](https://jcckit.sourceforge.net)
+
+## See more information on
+- [readme of `plantuml/jcckit`](../net/sourceforge/plantuml/jcckit/readme.md)

src/org/stathissideris/ascii2image/core/package-info.java

@@ -0,0 +1,16 @@
+/*
+ * ⚠ Disclaimer 🚩
+ * This file was not part of the original package.
+ * It was included only on the PlantUML package 
+ * to provide source citation and documentation.
+ *
+ */
+/**
+ * Internal copy of 
+ * <a href="https://github.com/stathissideris/ditaa" target="_top">
+ * <code>ditaa</code></a> <i>(code of Stathis Sideris)</i>.
+ * 
+ * @see net.sourceforge.plantuml.ditaa
+ * 
+ */
+package org.stathissideris.ascii2image.core;

src/org/stathissideris/ascii2image/core/readme.md

@@ -0,0 +1,15 @@
+> [!WARNING] 
+> **Disclaimer**:
+> This file was not part of the original package.
+> It was included only on the PlantUML package to provide source citation and documentation.
+
+# Directory Documentation for `core`
+
+## Description
+Internal copy of `ditaa` _(code of Stathis Sideris)_.
+
+## Credit
+- :octocat: [stathissideris/ditaa](https://github.com/stathissideris/ditaa)
+
+## See more information on
+- [readme of `plantuml/ditaa`](../../../../net/sourceforge/plantuml/ditaa/readme.md)

src/smetana/core/package-info.java

@@ -5,9 +5,9 @@
  * in <a href="https://plantuml.com/smetana02" target="_top">plantuml</a>.
  *
  * @see h
- * @see gen
+ * @see "gen"
  * @see gen.annotation
- * @see gen.lib
+ * @see "gen.lib"
  * @see gen.plugin.dot_layout
  * @see net.sourceforge.plantuml.sdot
  *