Bluesky scans: skeletal repository

Where?

As a developer I would like a skeletal ibex_bluesky_core repository, to act as a starting point for further pull requests.

[x] Minimal git repository created
- https://github.com/ISISComputingGroup/ibex_bluesky_core
[x] Local development process documented in a README or wiki or similar
[x] Bare minimum of functionality, just enough to give people a location to create future PRs onto
- Include python package structure boilerplate e.g. pyproject.toml, src and tests folders, obvious dependencies like bluesky and ophyd-async, and other miscellaneous python packaging infrastructure as required
- Include a small amount of skeletal bluesky code e.g. a very simple ophyd_async device for a block - but these will intentionally be "as simple as possible" as starting points for future tickets
- Exclude CI setup as that is being covered in https://github.com/ISISComputingGroup/ibex_bluesky_core/issues/1
[x] Create a small number of initial issues to progress this work
- Agreed with Kathryn these issues probably make sense to be in the ibex_bluesky_core repo - can still be pulled onto ibex project board from there
- See https://github.com/ISISComputingGroup/ibex_bluesky_core/issues
[x] Document a few early architectural decisions as markdown in an ADRs folder
- Use ophyd_async rather than ophyd
- Separate into ibex_bluesky_core (independent package, pip installable) and then beamline/technique specific code which uses ibex_bluesky_core as a dependency
- Run in-process for now (as opposed to in a worker process).

verbose instructions for reviewer to test changes (Add before making a PR)

1:11:30