get sphinx-gallery to render all examples

[neuromusic]

many of our examples exceed the readthedocs resource limits. based on benchmarking done by @mattcai, we need a solution that will build and render the docs with at least 12GB RAM 40min runtime.

Some options:

• get larger build resources on RTD (@neuromusic has been discussing this with RTD)
• build the docs on Netlify (approx $1000/mo)
• roll our own building & hosting solution on AWS