Add a new default method `description()` on `ToolProvider` that returns a short one-line description of the tool, or an empty `Optional` if no description is available.

Proposal:

    /**
     * {@return a short description of the tool, or an empty
     * {@code Optional} if no description is available}
     *
     * @apiNote It is recommended that the description fits into a single
     * line in order to allow creating concise overviews like the following:
     * <pre>{@code
     * jar
     * Create, manipulate, and extract an archive of classes and resources.
     * javac
     * Read Java declarations and compile them into class files.
     * jlink
     * Assemble a set of modules (...) into a custom runtime image.
     * }
     * </pre>
     *
     * @since 19
     */
    default Optional<String> description() {
        return Optional.empty();
    }