Add overview of modules

[sormuras]

Logbook

Module Table

123 modules are part of this project.
 99 declared modules: 9 main modules, 90 test modules including 10 in-module test modules
  4 external modules stored `.bach/external-modules`
 20 system modules provided by Java 16

module	version	category	tags
foo	0.1-ea	declared	main
foo.bar	0.1-ea	declared	main
foo.bar	0.1-ea	declared	test, in-module
java.base	16	system	mandated
java.xml	16	system	-
org.junit.jupiter	5.7.1	external
org.junit.jupiter.api	5.7.1	external
test.foo	0.1-ea	declared	test

Print

123 modules are part of this project.
 99 declared modules: 9 main modules, 90 test modules including 10 in-module test modules
  4 external modules stored `.bach/external-modules`
 20 system modules provided by Java 16

[sormuras]

Partly implemented in external program

bach/.bach/src/describe.java

Lines 23 to 45 in e2f2280

	if (arguments.isEmpty() || arguments.contains("modules")) {
	var externalModulesFinder = ModuleFinder.of(bach.path().externalModules());
	System.out.println();
	System.out.println("## Modules");
	System.out.println();
	System.out.println("### Declared Modules");
	System.out.println();
	System.out.println(describeModules(explorer.newModuleInfoFinder(bach.path().root())));
	System.out.println();
	System.out.println("### External Modules");
	System.out.println();
	System.out.println(describeModules(externalModulesFinder));
	System.out.println();
	System.out.println("### Missing External Modules");
	System.out.println();
	var names = explorer.listMissingExternalModules(externalModulesFinder);
	names.stream().map("- `%s`"::formatted).forEach(System.out::println);
	System.out.printf(" %d missing module%s%n", names.size(), names.size() == 1 ? "" : "s");
	System.out.println();
	System.out.println("### System Modules");
	System.out.println();
	System.out.println(describeModules(ModuleFinder.ofSystem()));
	}