[Build dll] Fix errors and added steps in docs

[mfdeveloper]

Hi there!

I found some problems to build the main C++ .dll to use with the wrappers (in my case, on .net). This PR contains some fixes to avoid the compiling errors.

Also, I added a step by step guide in docs/README.md to describe which dependencies you should install first, and how generate the .dll.

Besides that, I would like to suggest:

1. Publish/upload the all "packages" (e.g main .dll, .jar...) to Releases in this repository, and put the current stable version number
2. Merge and "adapt" the PR Build Tolk using CMake and publish artifacts using Github workflow #19 to use CMake to compile the C++ dll as a alternative to use nmake or jom with `Makefile's. That will be more easy to upgrade this project to a "cross platform" approach in the future 😄

[bear101]

Doesn't this cause a linker error?

I think what you want to do is this:
ScreenReaderDriver& operator=(const ScreenReaderDriver&) = delete;
to prevent copying.