docs: add GitHub Sponsors funding option

- Added GitHub Sponsors configuration file to enable sponsorship button
- Updated README to include GitHub Sponsors link alongside existing donation options
- Configured sponsorship to direct to Xe138's GitHub profile

.github/FUNDING.yml

@@ -0,0 +1,2 @@
+# GitHub Sponsors configuration
+github: Xe138

README.md

@@ -308,6 +308,8 @@ When reporting bugs, please include:
 
 If you find this plugin helpful, consider supporting its development:
 
+**GitHub Sponsors:** https://github.com/sponsors/Xe138
+
 **Buy Me a Coffee:** https://buymeacoffee.com/xe138
 
 ## License