Add entry for cytoscape-blink extension

Ref: List extension : cytoscape-blink nodes and edges #3134

documentation/md/extensions.md

@@ -23,6 +23,7 @@ The extensions below are a curated list.  To add your extension, [please submit
  * <i class="fa fa-fw fa-users"></i> [`anywhere-panning`](https://github.com/lambdalisue/cytoscape-anywhere-panning) : Allow panning when dragging on nodes or edges.
  * <i class="fa fa-fw fa-user"></i> [`automove`](https://github.com/cytoscape/cytoscape.js-automove) : Automatically update node positions based on specified rules (e.g. synching node movements, constraining movements, etc.)
  * <i class="fa fa-fw fa-user"></i> [`autopan-on-drag`](https://github.com/iVis-at-Bilkent/cytoscape.js-autopan-on-drag) : Automatically pan the viewport when nodes are dragged outside of the viewport bounds.
+ * <i class="fa fa-fw fa-users"></i> [`blink`](https://github.com/simCecca/cytoscape-blink) : Make elements blink.
  * <i class="fa fa-fw fa-users"></i> [`bubblesets`](https://github.com/sgratzl/cytoscape.js-bubblesets) : Visually group a set of elements via a [bubble set](https://ieeexplore.ieee.org/document/5290706).
  * <i class="fa fa-fw fa-users"></i> [`canvas`](https://github.com/classcraft/cytoscape.js-canvas) : An extension to create a canvas over or under a Cytoscape graph. Useful for customizing nodes/edges, drawing backgrounds, etc.
  * <i class="fa fa-fw fa-users"></i> [`cerebralweb`](https://github.com/silviafrias/cerebral-web) : Enable fast and interactive visualisation of molecular interaction networks stratified based on subcellular localisation or other custom annotation.