[jsscripting] Add an alternative MIME type/alias (#13851)

The alternative MIME type text/javascript is also used by Nashorn, therefore we add the same extension as for the main MIME type.
The alias is introduced to simplify the usage in SCRIPT transformation profiles.

* Fix syntax problems in the bndtools file
* Add null check to avoid potential NPE
  In some cases during testing, a NPE occured, this should solve it.

Signed-off-by: Florian Hotze <florianh_dev@icloud.com>

bundles/org.openhab.automation.jsscripting/bnd.bnd

@@ -1,9 +1,10 @@
 Bundle-SymbolicName: ${project.artifactId}
 DynamicImport-Package: *
 Import-Package: org.openhab.core.automation.module.script,javax.management,javax.script,javax.xml.datatype,javax.xml.stream;version="[1.0,2)",org.osgi.framework;version="[1.8,2)",org.slf4j;version="[1.7,2)"
-Require-Capability: osgi.extender;
+Require-Capability: 
+    osgi.extender:=
       filter:="(osgi.extender=osgi.serviceloader.processor)",
-    osgi.serviceloader;
+    osgi.serviceloader:=
       filter:="(osgi.serviceloader=org.graalvm.polyglot.impl.AbstractPolyglotImpl)";
       cardinality:=multiple