XML Formatter QoL improvements (#88)

- Rewritten backend methods for prettifing and minimizing XMLs
- Added "Clear" and "Insert default XML" buttons in XML Formatter.
- Added place to display error messages in case of any

Co-authored-by: Adam Bem <adam.bem@zoho.eu>
Reviewed-on: R11/release11-tools-web#88

Frontend/assets/css/tools/r11form.css

@@ -330,8 +330,8 @@
     height: 300px;
 }
 
-.textarea-800 {
-    height: 800px;
+.textarea-700 {
+    height: 700px;
 }
 
 .centered-content {