Restore select2 input functionality after Bootstrap 5 cleanup

- Restored select2 input type from earlier commit d4adf5e^
- Added select2 import to bootstrap5-editable.js bundle
- Updated demo with select2 example (requires select2 library)
- Enhanced README.md with comprehensive select2 documentation
- Includes support for static sources, AJAX sources, and advanced configuration
- Select2 library must be included separately (not bundled)

demo/index.html

@@ -63,6 +63,22 @@
                 </a>
             </div>
 
+            <div class="container">
+                <h3>Test X-Editable Select2</h3>
+                <p>Click to select from a larger list with search (Note: Requires select2 library):</p>
+
+                <a
+                    href="#"
+                    id="select2-test"
+                    class="editable editable-click"
+                    data-type="select2"
+                    data-pk="104"
+                    data-title="Select Country"
+                >
+                    Click to select country
+                </a>
+            </div>
+
         </form>
     </body>
 </html>