Modernize Select2 integration and fix popover page jumping

- Upgraded Select2 from bundled v3.4.4 (2013) to v4.x peer dependency
- Removed legacy Select2 v3.x bundled files from lib directory
- Updated Select2 input to use v4.x API (events, AJAX, templates)
- Fixed Bootstrap 5 popover page jumping issue with multi-timeout scroll restoration
- Added comprehensive migration documentation in README-select2-upgrade.md
- Rebuilt all distribution files with updated source code

Breaking Changes:
- Select2 now requires separate installation as peer dependency
- AJAX configuration updated for v4.x format
- Event names changed (select2:select vs select2-loaded)
- Template functions renamed (templateResult vs formatResult)

package.json

@@ -1,6 +1,6 @@
 {
-  "name": "@24unix/x-editable",
-  "title": "X-editable",
+  "name": "x-editable-bs5",
+  "title": "X-editable-bs5",
   "description": "A maintained fork of x-editable for Bootstrap 5 support.",
   "version": "1.5.2",
   "homepage": "https://git.24unix.net/tracer/x-editable",
@@ -41,6 +41,9 @@
     "popper.js": "^1.16.1",
     "webpack": "^5.98.0"
   },
+  "peerDependencies": {
+    "select2": "^4.0.0"
+  },
   "devDependencies": {
     "css-loader": "^7.1.2",
     "file-loader": "^6.2.0",