([Full Changelog](https://github.com/jupyterlab/jupyterlab/compare/v4.0.0a13...8c67f5949af19503e447a83584885f919e115c47))
Enhancements made
- Added button theme variables, updated button style [11264](https://github.com/jupyterlab/jupyterlab/pull/11264) ([3coins](https://github.com/3coins))
Bugs fixed
- Fix for debugger not working for scripts [11311](https://github.com/jupyterlab/jupyterlab/pull/11311) ([3coins](https://github.com/3coins))
- Added handling of '\r' ended files [11310](https://github.com/jupyterlab/jupyterlab/pull/11310) ([lucabarcelos](https://github.com/lucabarcelos))
- Emit `indexChanged` on model state updates [11298](https://github.com/jupyterlab/jupyterlab/pull/11298) ([krassowski](https://github.com/krassowski))
- Fix ANSI vs URL conflict, prefix `www.` with `https://` [#11272](https://github.com/jupyterlab/jupyterlab/pull/11272) ([krassowski](https://github.com/krassowski))
- Normalize cell source \r line endings [11271](https://github.com/jupyterlab/jupyterlab/pull/11271) ([jasongrout](https://github.com/jasongrout))
Maintenance and upkeep improvements
- Pass version spec as an input [11322](https://github.com/jupyterlab/jupyterlab/pull/11322) ([jtpio](https://github.com/jtpio))
- Added debugger UI tests for scripts [11319](https://github.com/jupyterlab/jupyterlab/pull/11319) ([3coins](https://github.com/3coins))
- Update the latest `lumino` packages [11281](https://github.com/jupyterlab/jupyterlab/pull/11281) ([jtpio](https://github.com/jtpio))
- Extension upgrade script: Avoid throwing exceptions for certain package.json files [11278](https://github.com/jupyterlab/jupyterlab/pull/11278) ([ammgws](https://github.com/ammgws))
- UI tests for debugger [11250](https://github.com/jupyterlab/jupyterlab/pull/11250) ([3coins](https://github.com/3coins))
- Run comparative benchmark [11128](https://github.com/jupyterlab/jupyterlab/pull/11128) ([fcollonval](https://github.com/fcollonval))
Documentation improvements
- Add note on weekly dev notes [11317](https://github.com/jupyterlab/jupyterlab/pull/11317) ([fcollonval](https://github.com/fcollonval))
- amend changelog - follow up issue 11304 [11309](https://github.com/jupyterlab/jupyterlab/pull/11309) ([achimgaedke](https://github.com/achimgaedke))
- update the binder sha to the latest demo version [11302](https://github.com/jupyterlab/jupyterlab/pull/11302) ([akhmerov](https://github.com/akhmerov))
- Add note on the server parameter for hidden files. [11293](https://github.com/jupyterlab/jupyterlab/pull/11293) ([fcollonval](https://github.com/fcollonval))
- Clarify sidebar switching settings [11270](https://github.com/jupyterlab/jupyterlab/pull/11270) ([joelostblom](https://github.com/joelostblom))
- Add missing changelog entry from 4.0.0a13 [11268](https://github.com/jupyterlab/jupyterlab/pull/11268) ([blink1073](https://github.com/blink1073))
- Run comparative benchmark [11128](https://github.com/jupyterlab/jupyterlab/pull/11128) ([fcollonval](https://github.com/fcollonval))
Contributors to this release
([GitHub contributors page for this release](https://github.com/jupyterlab/jupyterlab/graphs/contributors?from=2021-10-08&to=2021-10-20&type=c))
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