Switch css/less/scss to tm4e grammar/language config

[akurtakov]

Simplifies wildwebdeveloper development as the project will get the updates from tm4e without the need for CQs and etc.

[akurtakov]

@mickaelistria @vrubezhny I would appreciate your review if you have time.

[akurtakov]

Added the xsl switch as second commit as without it tests fail. There is some incompatibility which is visible even with master before this PR if one tries to run org.eclipse.wildwebdeveloper.tests.TestXML.testXSLFile with TM4e language pack installed the test fails with:

java.lang.ClassCastException: class org.eclipse.ui.internal.ErrorEditorPart cannot be cast to class org.eclipse.ui.texteditor.ITextEditor (org.eclipse.ui.internal.ErrorEditorPart is in unnamed module of loader org.eclipse.osgi.internal.loader.EquinoxClassLoader @64c3ca20; org.eclipse.ui.texteditor.ITextEditor is in unnamed module of loader org.eclipse.osgi.internal.loader.EquinoxClassLoader @637aaf98)
	at org.eclipse.wildwebdeveloper.tests.TestXML.testXSLFile(TestXML.java:98)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:727)
	at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
	at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:156)

just like on jenkins (https://ci.eclipse.org/wildwebdeveloper/job/Wildwebdeveloper/job/PR-1552/1/testReport/junit/org.eclipse.wildwebdeveloper.tests/TestXML/testXSLFile/) after the language pack makes it in the dependencies via the first commit of this PR.

[vrubezhny]

Looks good to me. Thanks!