Docs/guide about debugging crashes for java developers

[ktoso]

It's important to teach how java developers can debug crashes in swift.

E.g. a crash

     Stack: [0x000000016d7c8000,0x000000016d9cb000],  sp=0x000000016d9c5d10,  free space=2039k
     Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
     V  [libjvm.dylib+0x579b14]  jni_GetArrayLength+0x108
     C  [libSwiftJava.dylib+0x1a1dc4]  $sSa16SwiftJavaJNICoreAA0B5ValueRzlE7fromJNI2inSayxGSvSg_SpySPySo18JNINativeInterfaceVGSgGtcfC+0x118
     C  [libSwiftJava.dylib+0x1a4c24]  $sSayxG16SwiftJavaJNICore0B5ValueA2bCRzlAbCP7fromJNI2inx7JNITypeQz_SpySPySo18JNINativeInterfaceVGSgGtcfCTW+0x20
     C  [libSwiftJava.dylib+0x1a277c]  $sSa16SwiftJavaJNICoreAA0B5ValueRzlE7fromJNI2inSayxGSvSg_SpySPySo18JNINativeInterfaceVGSgGtcfcx7JNITypeQzXEfU2_+0xb8
     C  [libSwiftJava.dylib+0x1a27bc]  $sSa16SwiftJavaJNICoreAA0B5ValueRzlE7fromJNI2inSayxGSvSg_SpySPySo18JNINativeInterfaceVGSgGtcfcx7JNITypeQzXEfU2_TA+0x2c
     C  [libSwiftJava.dylib+0x1988]  $sSlsE3mapySayqd__Gqd__7ElementQzqd_0_YKXEqd_0_YKs5ErrorRd_0_r0_lF+0x400
     C  [libSwiftJava.dylib+0x1a2150]  $sSa16SwiftJavaJNICoreAA0B5ValueRzlE7fromJNI2inSayxGSvSg_SpySPySo18JNINativeInterfaceVGSgGtcfC+0x4a4
     C  [libMySwiftLibrary.dylib+0x36670]
     $s14MySwiftLibrary023Java_com_example_swift_abC29__00024nestedByteArray___3_3B11environment9thisClass5arraySvSgSpySPySo18JNINativeInterfaceVGSgGSg_SvAFtF+0xe8
     C  [libMySwiftLibrary.dylib+0x36580]  Java_com_example_swift_MySwiftLibrary__00024nestedByteArray___3_3B+0xc
     j  com.example.swift.MySwiftLibrary.$nestedByteArray([[B)[[B+0
     j  com.example.swift.MySwiftLibrary.nestedByteArray([[B)[[B+9
     j  com.example.swift.ArraysTest.lambda$nestedByteArray_null$1()V+24
     j  com.example.swift.ArraysTest$$Lambda+0x0000060001166dc0.execute()V+0
     j  org.junit.jupiter.api.AssertThrows.assertThrows(Ljava/lang/Class;Lorg/junit/jupiter/api/function/Executable;Ljava/lang/Object;)Ljava/lang/Throwable;+1
     j  org.junit.jupiter.api.AssertThrows.assertThrows(Ljava/lang/Class;Lorg/junit/jupiter/api/function/Executable;)Ljava/lang/Throwable;+3
     j  org.junit.jupiter.api.Assertions.assertThrows(Ljava/lang/Class;Lorg/junit/jupiter/api/function/Executable;)Ljava/lang/Throwable;+2
     j  com.example.swift.ArraysTest.nestedByteArray_null()V+18

can be demangled using cat ... | swift demangle but java developers may not know about this etc.