Fix auto scrolling issue in debugger on step in and step out. Fixes #3554.

web/pgadmin/static/js/codemirror/extension/centre_on_line.js

@@ -0,0 +1,7 @@
+import CodeMirror from 'codemirror/lib/codemirror';
+
+CodeMirror.defineExtension('centerOnLine', function(line) {
+  var ht = this.getScrollInfo().clientHeight;
+  var coords = this.charCoords({line: line, ch: 0}, 'local');
+  this.scrollTo(null, (coords.top + coords.bottom - ht) / 2);
+});