text: Title: [FEA] GFQL benchmark notebook and GPU examples
  Body: **Is your feature request related to a problem? Please describe.**
  
  I added discussion of GFQL GPU support to the main readme and doc strings, but we should have some accessible ipynb's
  
  **Describe the solution you'd like**
  
  - [x] **simple** ipynb showing a before/after speedup of gfql (e.g., 4 very short & simple cells)
    - mention using hop() for more speedups for simpler task
    - clear 10X+ win on the benchmark
    - show it works just by passing in cudf.DataFrame, and optionally, setting `engine='cudf'`
  - [x] also cleaned up version of our bigger benchmark one: https://colab.research.google.com/drive/1iuH9YWd3VLSALR-3z1Jt35MXELI3Sjk_#scrollTo=bK4C9Ly0hso-
  - [x] linked in the gfql section(s) in the readme.md as appropriate
  
  
  **Additional context**
  
  Let's land cucat first..