qxrun script location not ideal for user projects

[brenjohn]

At the moment, if a user wants to add QXContexts to their project and use the qxrun script from within their project, they'll need to specify the path the QXContexts package in their .julia/packages/... directory.

We could add a build step to place it somewhere more convenient when QXContext is added or add a generate_qxrun_script function to add the script to the bin directory of their project.

There's also an argument for qxrun in the tutorial, for setting the number of blas threads, which isn't available on the master branch. Perhaps we should add this as a new argument or remove it from the tutorial.
https://juliaqx.github.io/QXTools.jl/dev/distributed/#Measuring-the-time-and-speedup