set up depot downloader

scripts/setup_depot_downloader.sh

@@ -0,0 +1,21 @@
+REPO_USER="SteamRE"
+REPO_NAME="DepotDownloader"
+TEMP="temp"
+
+OUT="$TEMP/$REPO_NAME"
+ZIP="$TEMP/$REPO_NAME.zip"
+
+URL=$(
+  curl -s "https://api.github.com/repos/$REPO_USER/$REPO_NAME/releases/latest" \
+    | jq -r '.assets[]
+      | select(.name | contains("linux-x64"))
+      | .browser_download_url' \
+    | head -n 1
+)
+
+mkdir -p "$TEMP"
+curl -L "$URL" -o "$ZIP"
+unzip -p "$ZIP" "$REPO_NAME" > "$OUT"
+rm "$ZIP"
+
+chmod +x "$OUT"