Improving the project with opencv_contrib

[kalwalt]

I will works in this PR on this tasks:

• improving the script to compile opencv with the external module opencv_contrib
• adding as submodules our opencv and opencv_contrib forks
• provide an github action script to compile and make a new relase with uploaded the libs, headers and all required to compile webarkit.

For more informations see PR https://github.com/webarkit/WebARKitLib/pull/19

[kalwalt]

Now the script sohould be capable to build the emscripten and standard (linux) static libs. I will try to set up a github action to test the script and eventually make an automatic release, so everyone can download the zipped static libs.

[kalwalt]

The build script fails creating the opencv_java shared lib, on my local machine doesn't happens ( maybe because i have not the required libs for java?), so i will force to disable the java module and rerun the build script.

[kalwalt]

Ok now all the libs are built but the action script fails with this message:

Opencv.js and static libs successfully built!
Packagings libs and includes in a .zip file...
rsync: [sender] change_dir "/home/runner/work/opencv-em/opencv-em/opencv_js" failed: No such file or directory (2)
rsync error: errors selecting input/output files, dirs (code 3) at flist.c(2244) [sender=3.2.7]
rsync error: received SIGUSR1 (code 19) at main.c(1613) [Receiver=3.2.7]
Error: Process completed with exit code 3.

I will fix soon.

[kalwalt]

Now the script is succesful, but i discovered that the xfeatures2d module is not built.

[kalwalt]

Now because the github action script is succesful i will try to add the .zip files to every new release, so an user can download the pre-built libs.

[kalwalt]

I have tested the compiled files, all is fine, tested WebARKitLib/tests with this gist