Improve render performance (#511)

Massive improvement of render performance by:
- replacing the codimd-line-marker with an in-memory map
- an observation of the changed markdown code to identify changed lines
- a unique react-key calculation

src/components/markdown-renderer/replace-components/vimeo/vimeo-replacer.tsx

@@ -4,16 +4,16 @@ import { getAttributesFromCodiMdTag } from '../codi-md-tag-utils'
 import { ComponentReplacer } from '../ComponentReplacer'
 import { VimeoFrame } from './vimeo-frame'
 
-export class VimeoReplacer implements ComponentReplacer {
+export class VimeoReplacer extends ComponentReplacer {
   private counterMap: Map<string, number> = new Map<string, number>()
 
-  getReplacement (node: DomElement): React.ReactElement | undefined {
+  public getReplacement (node: DomElement, index: number): React.ReactElement | undefined {
     const attributes = getAttributesFromCodiMdTag(node, 'vimeo')
     if (attributes && attributes.id) {
       const videoId = attributes.id
       const count = (this.counterMap.get(videoId) || 0) + 1
       this.counterMap.set(videoId, count)
-      return <VimeoFrame key={`vimeo_${videoId}_${count}`} id={videoId}/>
+      return <VimeoFrame key={index} id={videoId}/>
     }
   }
 }