* Add .DS_Store to .gitignore
* Factor out bonito-core and bonito-ui
These packages are intended to act as a Batch-agnostic layer
for building Azure Portal-compatible UIs.
This also moves much of the functionality of the ui-service
package into bonito-core (specifically the parts that aren't
Batch-specific)
* Make `bux link` handle missing packages in node_modules
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Co-authored-by: Sanjana Kapur <sanjanakapur@microsoft.com>