add toUpper and bounding box sanitizer

src/customSanitizers.js

 const toLower = (value) => {
-  if(!value) return;
+  if (!value) return;
   return value.toLowerCase();
 }
 
-module.exports = { toLower };
+const toUpper = (value) => {
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+  if (!value) return;
+  return value.toUpperCase();
+}
+
+const boundingboxIsValid = (value) => {
+  let tokens = value.split(",");
+  tokens = tokens.map(token => parseFloat(token));
+  if (tokens[0] < tokens[2] && tokens[1] < tokens[3]) {
+    return true;
+  }
+  return false;
+
+}
+
+module.exports = { toLower, toUpper, boundingboxIsValid };
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