[J8] Add manual loading example description

Author: temikfart

img/Java 8. Manual Loading.jpg

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+## Java 8. Manual Loading
+---
+**Task:** load any application class using a custom class loader (`CustomClassLoader`).
+
+### Solution
+---
+Project with three classes:
+- [`Main`](src/ru/ispras/j8/manual/Main.java) - a class containing the `main` method, where an instance of the `CustomClassLoader` class is created, the `Cat` class is loaded using it, creating an instance of the class `Cat` and calling the `Cat::talk` method;
+- [`Cat`](src/ru/ispras/j8/manual/Cat.java) - loadable class with the `talk` method, which prints the string *"Meow"* to `stdout`;
+- [`CustomClassLoader`](src/ru/ispras/j8/manual/CustomClassLoader.java) - a class that is an implementation of a custom class loader.
+
+### Run
+---
+```shell
+java8 -cp . ru.ispras.j8.manual.Main
+```
+
+or
+
+```shell
+java8 -jar manual-1.0.jar
+```
+
+Output:
+
+```
+System ClassLoader is ru.ispras.j8.manual.CustomClassLoader@75b84c92
+Main Class ClassLoader is ru.ispras.j8.manual.CustomClassLoader@75b84c92
+Cat Class ClassLoader is ru.ispras.j8.manual.CustomClassLoader@75b84c92
+Meow
+```
+
+### Explanation
+---
+![Java 8. Manual Loading.jpg](../../img/Java%208.%20Manual%20Loading.jpg)
+
+- When a `CustomClassLoader` is created, its parent becomes `sun.misc.Launcher$AppClassLoader`.
+
+### Notes
+---
+- `CustomClassLoader` gets some system classes to be loaded first, for example classes from `java.*` packages. If you try to load a class from the `java.*` package, the JVM will throw `java.lang.SecurityException: Prohibited package name: java.*`.