Add methods to set width/height programatically

tp-vsplitter.js

@@ -97,6 +97,10 @@ class TpVSplitter extends LitElement {
     document.body.style['userSelect'] = '';
   }
 
+  setWidth(width) {
+    this.style.gridTemplateColumns = `${width} var(--tp-splitter-width, 5px) 1fr`;
+  }
+
   _enableDrag(e) {
     document.addEventListener('mouseup', this._disableDrag)
     document.addEventListener('mousemove', this._resize);