OPENNLP-1850 Clarify that Extended_Pictographic symbols are kept as emoji

WordType classifies every Extended_Pictographic code point as EMOJI, which
includes symbol-like characters (copyright, trademark, double-exclamation,
arrows), so the word tokenizer keeps them rather than dropping them as
punctuation. State this in the WordTokenizer javadoc and add a test.

Author: krickert

opennlp-core/opennlp-runtime/src/main/java/opennlp/tools/tokenize/uax29/WordTokenizer.java

@@ -26,7 +26,9 @@
  * A word tokenizer built on the Unicode Text Segmentation algorithm (UAX #29). It finds segments
  * with {@link WordSegmenter}, keeps the ones that are words (letters, digits, ideographs, kana,
  * Hangul, Southeast-Asian script, or emoji), drops whitespace and punctuation, and classifies each
- * kept token with a {@link WordType}.
+ * kept token with a {@link WordType}. Emoji here means any {@code Extended_Pictographic} code point,
+ * so symbol-like characters such as the copyright, trademark, and double-exclamation signs are kept
+ * (typed {@link WordType#EMOJI}) rather than dropped as punctuation.
  *
  * <p>A token longer than {@code maxTokenLength} is emitted as consecutive pieces, never splitting a
  * surrogate pair. The tokenizer reports offset {@link Span}s, so the original text and its character

opennlp-core/opennlp-runtime/src/test/java/opennlp/tools/tokenize/uax29/WordTokenizerTest.java

@@ -89,6 +89,18 @@ void testKatakanaRunStaysTogether() {
     assertEquals(text, tokens.get(0).text(text));
   }
 
+  @Test
+  void testExtendedPictographicSymbolsAreKeptAsEmoji() {
+    // Extended_Pictographic includes symbol-like characters (copyright U+00A9, trademark U+2122,
+    // double exclamation U+203C), which WordType classifies as EMOJI, so the tokenizer keeps them
+    // rather than dropping them as punctuation.
+    final String text = "a " + cp(0x00A9) + " " + cp(0x2122) + " " + cp(0x203C) + " b";
+    final List<WordToken> tokens = TOKENIZER.tokenizeTyped(text);
+    assertEquals(List.of(WordType.ALPHANUMERIC, WordType.EMOJI, WordType.EMOJI,
+            WordType.EMOJI, WordType.ALPHANUMERIC),
+        tokens.stream().map(WordToken::type).toList());
+  }
+
   @Test
   void testHangulSyllablesStayTogether() {
     final String text = cp(0xAC00) + cp(0xB098); // ga + na