Fix schemaZip Gradle task on MS Windows

Prior to this commit, the schemaZip Gradle task failed to find Spring
schema files on MS Windows due to path separators hard coded to forward
slashes that are not compatible with the Windows operating system.

Consequently, a full build failed on Windows since the distZip task was
not able to locate the zipped schema archive that the schemaZip task
failed to create.

This commit fixes this by updating the schemaZip task to search for
schema files using backslashes as well as forward slashes.

Closes gh-23933

gradle/docs.gradle

@@ -148,14 +148,14 @@ task schemaZip(type: Zip) {
 		def Properties schemas = new Properties();
 
 		subproject.sourceSets.main.resources.find {
-			it.path.endsWith("META-INF/spring.schemas")
+			(it.path.endsWith("META-INF/spring.schemas") || it.path.endsWith("META-INF\\spring.schemas"))
 		}?.withInputStream { schemas.load(it) }
 
 		for (def key : schemas.keySet()) {
 			def shortName = key.replaceAll(/http.*schema.(.*).spring-.*/, '$1')
 			assert shortName != key
 			File xsdFile = subproject.sourceSets.main.resources.find {
-				it.path.endsWith(schemas.get(key))
+				(it.path.endsWith(schemas.get(key)) || it.path.endsWith(schemas.get(key).replaceAll('\\/','\\\\')))
 			}
 			assert xsdFile != null
 			into (shortName) {