feat: add JMH comparison benchmarks for Radixor vs Snowball Porter stemmers

build: isolate Snowball benchmark integration into dedicated Gradle script
docs: highlight benchmarked throughput advantage in README
docs: add detailed benchmarking guide and execution notes

build.gradle

@@ -125,7 +125,7 @@ jmh {
 
 tasks.named('jmh') {
     group = 'verification'
-    description = 'Runs JMH benchmarks for the Radixor algorithmic core.'
+    description = 'Runs JMH benchmarks for the Radixor algorithmic core and Snowball comparison suite.'
 }
 
 javadoc {
@@ -154,6 +154,8 @@ javadoc {
     source = sourceSets.main.allJava
 }
 
+apply from: 'gradle/snowball-benchmarks.gradle'
+
 gradle.taskGraph.whenReady { taskGraph ->
     def banner = """
 \u001B[34m