chore(pack): add .packwizignore for server-generated files

Keeps the NeoForge libraries, world data, jars and other runtime files
out of the pack index when running packwiz refresh in a server dir.

.packwizignore

@@ -0,0 +1,13 @@
+# Server/runtime files - never track these in the pack index
+libraries/
+world*/
+logs/
+crash-reports/
+eula.txt
+options.txt
+server.properties
+user_jvm_args.txt
+run.sh
+*.jar
+*.jar.log
+run.bat