specify utf8 encoding

this should fix the following known bugs:
 - putting a U+2019 in the config causes it to become corrupted and
   ~double in size every launch
 - scripts become assembled incorrectly and the nbsp after your name in
   the chatbox becomes incorrect
 - the feed panel doesn't show emoji

cache/src/test/java/net/runelite/cache/script/assembler/AssemblerTest.java

@@ -25,6 +25,7 @@
 package net.runelite.cache.script.assembler;
 
 import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
 import net.runelite.cache.definitions.ScriptDefinition;
 import net.runelite.cache.script.Instructions;
 import net.runelite.cache.script.disassembler.Disassembler;
@@ -76,7 +77,7 @@ public class AssemblerTest
 		in = AssemblerTest.class.getResourceAsStream(this.script);
 		Assert.assertNotNull(in);
 
-		String original = new String(IOUtils.toByteArray(in)).replaceAll("\r\n", "\n");
+		String original = new String(IOUtils.toByteArray(in), StandardCharsets.UTF_8).replaceAll("\r\n", "\n");
 
 		logger.info(original);
 		logger.info("-----------------------");

cache/src/test/java/net/runelite/cache/script/disassembler/DisassemblerTest.java

@@ -27,6 +27,7 @@ package net.runelite.cache.script.disassembler;
 import com.google.common.io.Files;
 import java.io.File;
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import net.runelite.cache.IndexType;
 import net.runelite.cache.StoreLocation;
 import net.runelite.cache.definitions.ScriptDefinition;
@@ -78,7 +79,7 @@ public class DisassemblerTest
 				Disassembler disassembler = new Disassembler();
 				String out = disassembler.disassemble(script);
 
-				Files.write(out.getBytes(), outFile);
+				Files.write(out.getBytes(StandardCharsets.UTF_8), outFile);
 
 				++count;
 			}

cache/src/test/java/net/runelite/cache/util/XteaTest.java

@@ -24,6 +24,7 @@
  */
 package net.runelite.cache.util;
 
+import java.nio.charset.StandardCharsets;
 import static org.junit.Assert.assertArrayEquals;
 import org.junit.Test;
 
@@ -32,7 +33,7 @@ public class XteaTest
 	@Test
 	public void test()
 	{
-		byte[] data = "testtesttest1".getBytes();
+		byte[] data = "testtesttest1".getBytes(StandardCharsets.UTF_8);
 
 		int[] key = new int[]
 		{