Expose ICU's `u_charDirection` function (#694)

* Expose u_charDirection

* Move CharDirection to icu package

* Add doc comment for CharDirection

skiko/src/commonMain/kotlin/org/jetbrains/skia/icu/Unicode.kt

+package org.jetbrains.skia.icu
+
+import org.jetbrains.skia.ExternalSymbolName
+import org.jetbrains.skia.impl.Library.Companion.staticLoad
+
+/**
+ * CharDirection represents Bidi_Class Unicode character property.
+ * Numeric constant values match to ICU's UCharDirection enum.
+ *
+ * See https://unicode-org.github.io/icu-docs/apidoc/dev/icu4c/uchar_8h.html
+ * See https://www.unicode.org/reports/tr9/
+ */
+object CharDirection {
+    init {
+        staticLoad()
+    }
+
+    const val LEFT_TO_RIGHT = 0
+    const val RIGHT_TO_LEFT = 1
+    const val EUROPEAN_NUMBER = 2
+    const val EUROPEAN_NUMBER_SEPARATOR = 3
+    const val EUROPEAN_NUMBER_TERMINATOR = 4
+    const val ARABIC_NUMBER = 5
+    const val COMMON_NUMBER_SEPARATOR = 6
+    const val BLOCK_SEPARATOR = 7
+    const val SEGMENT_SEPARATOR = 8
+    const val WHITE_SPACE_NEUTRAL = 9
+    const val OTHER_NEUTRAL = 10
+    const val LEFT_TO_RIGHT_EMBEDDING = 11
+    const val LEFT_TO_RIGHT_OVERRIDE = 12
+    const val RIGHT_TO_LEFT_ARABIC = 13
+    const val RIGHT_TO_LEFT_EMBEDDING = 14
+    const val RIGHT_TO_LEFT_OVERRIDE = 15
+    const val POP_DIRECTIONAL_FORMAT = 16
+    const val DIR_NON_SPACING_MARK = 17
+    const val BOUNDARY_NEUTRAL = 18
+    const val FIRST_STRONG_ISOLATE = 19
+    const val LEFT_TO_RIGHT_ISOLATE = 20
+    const val RIGHT_TO_LEFT_ISOLATE = 21
+    const val POP_DIRECTIONAL_ISOLATE = 22
+
+    /**
+     * Returns the bidirectional category value for the code point.
+     * Same as java.lang.Character.getDirectionality()
+     */
+    fun of(codePoint: Int): Int = charDirection(codePoint)
+}
+
+@ExternalSymbolName("org_jetbrains_skia_icu_Unicode_charDirection")
+private external fun charDirection(codePoint: Int): Int

skiko/src/commonTest/kotlin/org/jetbrains/skia/icu/UnicodeTest.kt

+package org.jetbrains.skia.icu
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class UnicodeTest {
+
+    @Test
+    fun directionality() {
+        assertEquals(CharDirection.EUROPEAN_NUMBER, CharDirection.of('0'.code)) // Number
+        assertEquals(CharDirection.LEFT_TO_RIGHT, CharDirection.of('A'.code)) // Latin
+        assertEquals(CharDirection.RIGHT_TO_LEFT, CharDirection.of('א'.code)) // Hebrew
+        assertEquals(CharDirection.RIGHT_TO_LEFT_ARABIC, CharDirection.of('؈'.code)) // Arabic
+    }
+}
\ No newline at end of file

skiko/src/jvmMain/cpp/common/icu/Unicode.cc

+#include <jni.h>
+#include "third_party/externals/icu/source/common/unicode/uchar.h"
+
+extern "C" JNIEXPORT jint JNICALL Java_org_jetbrains_skia_icu_UnicodeKt_charDirection
+  (JNIEnv* env, jclass jclass, jint codePoint) {
+    return u_charDirection(codePoint);
+}

skiko/src/nativeJsMain/cpp/icu/Unicode.cc

+#include "common.h"
+#include "third_party/externals/icu/source/common/unicode/uchar.h"
+
+SKIKO_EXPORT KInt org_jetbrains_skia_icu_Unicode_charDirection(KInt codePoint) {
+    return u_charDirection(codePoint);
+}