add Bitbucket to home page

https://cml.dev/ "CML Use Cases" only has GH & GL (missing BB) runners.

- [x] add Bitbucket tab to https://github.com/iterative/cml.dev/blob/master/src/components/pages/Home/UseCasesSection/index.tsx (#362)
+ [ ] sort out demo repos https://github.com/iterative/cml-examples-dev/issues/9
+ [x] basic demo repo (https://bitbucket.org/iterative-ai/cml-base-case, also used in https://cml.dev/doc/usage?tab=Bitbucket)
+ [x] DVC demo repo (https://bitbucket.org/iterative-ai/cml-example-dvc?)
* [x] use in home page #362
* [x] #379
+ [x] Tensorboard demo repo (https://bitbucket.org/iterative-ai/cml-example-tensorboard?)
+ [x] Runner demo repo (https://bitbucket.org/iterative-ai/cml-cloud-case?)
+ [x] fixup home page #408
+ [ ] Runner GPU demo repo https://github.com/iterative/cml/issues/1015
* [x] use LEO directly https://github.com/iterative/cml.dev/issues/367? (https://github.com/iterative/cml-examples-dev/pull/24)
* [ ] update home page #410
- [x] https://github.com/iterative/cml.dev/pull/380