message: use PurePluginUIComponent for Residue
diff: import * as React from 'react'
  import { Structure, StructureSequence, Queries, StructureSelection, StructureProperties as SP, StructureQuery, StructureElement, Unit } from '../../mol-model/structure';
  -import { PluginUIComponent } from './base';
  +import { PluginUIComponent, PurePluginUIComponent } from './base';
  import { StateTreeSpine } from '../../mol-state/tree/spine';
  import { PluginStateObject as SO } from '../state/objects';
  import { Interactivity } from '../util/interactivity';
  @@ -240,7 +240,7 @@ class EntitySequence extends PluginUIComponent<EntitySequenceProps, EntitySequen
  }
  }
  -class Residue extends PluginUIComponent<{ seqId: number, letter: string, parent: EntitySequence, marker: number }> {
  +class Residue extends PurePluginUIComponent<{ seqId: number, letter: string, parent: EntitySequence, marker: number }> {
  mouseEnter = (e: React.MouseEvent) => {
  const modifiers = getModifiers(e.nativeEvent)
  