StereoBM bindings are missing

StereoBM bindings seem to be missing; they also seem to have changed a lot recently.

Citing OpenCV 3.4 docs as most relevant:
https://docs.opencv.org/3.4.4/d9/dba/classcv_1_1StereoBM.html

I am looking to use `create` and `compute`:
`create`: https://docs.opencv.org/3.4.4/d9/dba/classcv_1_1StereoBM.html#a04fdf00525f82fe708d556e2cd359004
`compute`: https://docs.opencv.org/3.4.4/d2/d6e/classcv_1_1StereoMatcher.html#a03f7087df1b2c618462eb98898841345

I also noticed https://github.com/justadudewhohacks/opencv4nodejs/issues/191#issuecomment-372105905

> The package does not have bindings to all modules and functionality of the OpenCV and OpenCV contrib API, this is the ultimate goal and would be nice to achieve. So far the package has bindings to the extra modules: face, tracking, text, xfeatures2d and ximgproc.
>
> If you want to use modules, that are not existing in the package yet and it's not that urgent, I can add bindings for you in the next release or optimally, if you feel confident to submit a PR, contribution is always highly appreciated :)

Do you have a good example of writing bindings?
I have found this package to be much more pleasant than using Python bindings 😃