update scripts folder

Change steamcmd recommended to debian-buster-slim
Update release grabber with curly braces on variables (readability).
Add script for validating that download links actually exist with no errors.
update gitignore.

scripts/download_link_validator.sh

@@ -0,0 +1,11 @@
+## this is a simple script to validate a download url actaully exists
+
+if [ ! -z "${DOWNLOAD_URL}"]; then 
+    if curl --output /dev/null --silent --head --fail ${DOWNLOAD_URL}; then
+        echo -e "link is valid. setting download link to ${DOWNLOAD_URL}"
+        DOWNLOAD_LINK=${DOWNLOAD_URL}
+    else        
+        echo -e "link is invalid closing out"
+        exit 2
+    fi
+fi