Merge pull request #18064 from akineeic:gsoc_2020_dnn

[GSoC] Develop OpenCV.js DNN modules for promising web use cases together with their tutorials

* [Opencv.js doc] Init commit to add image classification example in opencv.js tutorial

* [Opencv.js doc] Make the code snippet interactive and put the functions into code snippet.

* Fix the utils.loadOpenCv for promise module

* [Opencv.js doc] Code modify and fixed layout issue.

* [Opencv.js doc] Add a JSON file to store parameters for models and show in the web page.

* [Opencv.js doc] Change let to const.

* [Opencv.js doc] Init commit to add image classification example with camera in opencv.js tutorial

* [Opencv.js doc] Init commit to add semantic segmentation example in opencv.js tutorial

* [Opencv.js doc] Add object detection example, supprot YOLOv2

* [Opencv.js doc] Support SSD model for object detection example

* [Opencv.js doc] Add fast neural style transfer example with opencv.js

* [Opencv.js doc] Add pose estimation example in opencv.js tutorial

* Delete whitespace for code check

* [Opencv.js doc] Add object detection example with camera

* [Opencv.js doc] Add json files containing model information to each example

* [Opencv.js doc] Add a js file for common function in dnn example

* [Opencv.js doc] Create single function getBlobFromImage

* [Opencv.js doc] Add url of model into webpage

* [OpenCV.js doc] Update UI for running

* [Opencv.js doc] Load dnn model by input button

* [Opencv.js doc] Fix some UI issues

* [Opencv.js doc] Change code format

Co-authored-by: Ningxin Hu <ningxin.hu@intel.com>

doc/js_tutorials/js_tutorials.markdown

@@ -26,3 +26,7 @@ OpenCV.js Tutorials {#tutorial_js_root}
 
     In this section you
     will object detection techniques like face detection etc.
+
+-   @subpage tutorial_js_table_of_contents_dnn
+
+    These tutorials show how to use dnn module in JavaScript