docs: add aisample notebooks into community folder (#1606)

* docs: add aisample fraud detection

* docs: add aisample book recommendation

* chore: format notebooks with black and clear outputs

* chore: some improvements to code and annotations

* chore: remove random data in synapse metadata to reduce file size

* chore: update lib, neaten code

* chore: neaten code

* chore: remove default None params

* chore: improve scale perf with StringIndexer, remove params default None

* update notebook converter to only pick up notebooks in features folder

Co-authored-by: Li Jiang <lijiang1@microsoft.com>
Co-authored-by: Xinyue Ruan <serena.rxy@gmail.com>
Co-authored-by: Mark Hamilton <mhamilton723@gmail.com>