feat: constrain mousedown to left clicks

Only respond to mouse main button clicks (usually the left button).

https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/button

close #277

Author: andreruffert

src/rangeslider.js

@@ -316,6 +316,10 @@
 
     Plugin.prototype.handleDown = function(e) {
         e.preventDefault();
+        
+        // Only respond to mouse main button clicks (usually the left button)
+        if (e.button && e.button !== 0) return;
+        
         this.$document.on(this.moveEvent, this.handleMove);
         this.$document.on(this.endEvent, this.handleEnd);