add nashorn installation steps to Script transform docs. fixes apache…

…#4038

docs/hop-user-manual/modules/ROOT/pages/pipeline/transforms/script.adoc

@@ -29,10 +29,12 @@ The Script transform allows you to write code in any language supported by the h
 
 By default, the Hop project ships with the following language support:
 
-* ECMAScript (JavaScript as part of the JVM)
 * https://groovy-lang.org/[Groovy]
 * https://www.python.org/[Python] (https://www.jython.org/[Jython])
 
+WARNING: ECMAScript (JavaScript as part of the JVM) was removed from the JVM with Java 17. You can still add it in Apache Hop 2.10 and later as documented in the <<_adding_scripting_languages, Adding Scripting Languages>> section.
+
+
 |
 == Supported Engines
 [%noheader,cols="2,1a",frame=none, role="table-supported-engines"]
@@ -250,4 +252,9 @@ For example, to add support for the Ruby scripting language you need to add the
 * `jruby-stdlib-<version>.jar`
 * `jruby-core-<version>.jar`
 
-After restarting the Apache Hop GUI you'll notice that there's a `ruby` entry in the `Scripting Engine` dropdown box.
+To add Javascript support, download the https://repo1.maven.org/maven2/org/openjdk/nashorn/nashorn-core/[Nashorn Core jar]
+
+* `nashorn-core-15.4.jar`
+
+
+After restarting the Apache Hop GUI you'll notice that there's a `ruby` or `Javascript` entry in the `Scripting Engine` dropdown box.