Add *nix pack mode switcher (#128)

* Add *nix pack mode switcher

* Actually implement mode switching properly

* Add instructions for *nix pack mode switcher

* Add flag-based operation

* Quote mode in case

README.md

@@ -32,6 +32,7 @@ If you want a harder, or perhaps a more "true" GregTech experience, check out th
 Installation instructions:
 - Install the hardmode config files from [here](https://github.com/tracer4b/nomi-ceu/tree/main/overrides). Restart the pack for this to take effect. 
   - Windows users may grab the utility [here](https://raw.githubusercontent.com/tracer4b/nomi-ceu/main/pack-mode-switcher.bat)(right click - save as), save it to the root directory of the pack (the same level as `\config`). 
+  - MacOS and GNU/Linux users can run `curl -s https://raw.githubusercontent.com/tracer4b/nomi-ceu/main/pack-mode-switcher.sh | sh` in the pack root directory (the one containing `/config`).
 - If you are on an existing world, run `/bq_admin default load` to load the hard mode questbook.
 
 ## Credits

pack-mode-switcher.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env sh
+set -e
+echo -e "Nomifactory GTCEu Port / Pack mode switcher"
+
+NORMAL_CFG=./config-overrides/normal
+EXPERT_CFG=./config-overrides/expert
+TARGET=./config
+
+if [ -z "$1" ]; then
+  echo -en "Set pack mode (Normal / Expert): "
+  read MODE
+else
+  MODE="$1"
+fi
+
+case "$MODE" in
+  N|n|normal)
+    cp -rf "$NORMAL_CFG"/* "$TARGET"
+    rm -f "$TARGET/globalgamerules.cfg"
+  ;;
+
+  E|e|expert)
+    cp -rf "$EXPERT_CFG"/* "$TARGET"
+  ;;
+
+  *)
+    echo -e "Error: Invalid mode $MODE"
+    exit 1
+  ;;
+esac
+
+echo "Done!"