feat: remove default configuration to prevend accidental override.

we used to have file neko.yaml with default configuration, but if we would add neko.yml the default configuration would still be read. so instead, default configuartion was moved to the sever itself and no file is distributed with it by defautl.

server/dev/start

@@ -61,7 +61,8 @@ docker run --rm -it \
     -e "NEKO_WEBRTC_TCPMUX=${NEKO_MUX}" \
     -e "NEKO_WEBRTC_NAT1TO1=${NEKO_NAT1TO1}" \
     -e "NEKO_SESSION_FILE=/home/neko/sessions.txt" \
-    -v "${PWD}/runtime/$CONFIG:/etc/neko/neko.yml" \
+    -e "NEKO_SERVER_CORS=*" \
+    -v "${PWD}/runtime/$CONFIG:/etc/neko/neko.yaml" \
     -e "NEKO_DEBUG=1" \
     --shm-size=2G \
     --security-opt seccomp=unconfined \