Add option to use static runtime

[computerquip-streamlabs]

There appears to have been misconception of not being able to use /MD when using libcef. This isn't true due to the use of the libcef_dll_wrapper described here.

This adds an option to dynamically link against the runtime by setting BROWSER_USE_STATIC_CRT to a falsey value.

While I've set the default value here to true, I don't suggest statically against the runtime here at all. I've set it to default only because this is how it was already set and it felt less intrusive.