Bsl

- Add support for stream type `signal` used by OpenViBE servers to the `StreamReceiver`

**Full Changelog**: https://github.com/bsl-tools/bsl/compare/0.5.0...0.5.1

---------

This is the last release with the legacy API: `StreamPlayer`, `StreamReceiver`, `StreamRecorder`.
**The next release will be backward incompatible.** It will:
- replace `pylsl` with a new `lsl` module, dropping support for old versions of `python` and `liblsl` while improving greatly the performance, especially to pull chunks of data from the network
- replace the `StreamPlayer` with a `Player` API
- replace the `StreamReceiver` with a `Stream` API, with similar methods to an MNE object
- replace the `StreamRecorder` with a `Recorder` API, writing to disk as soon as the data is received

Please pin the version to `bsl < 0.6.0` if you need to retain the legacy API.

What's Changed
* Add black formatting and isort by mscheltienne in https://github.com/bsl-tools/bsl/pull/61
* [MNT] Move package configuration and dependencies to pyproject.toml by mscheltienne in https://github.com/bsl-tools/bsl/pull/62
* Bump liblsl, pylsl and psychopy versions in externals by mscheltienne in https://github.com/bsl-tools/bsl/pull/63
* Add LSLTrigger for triggers on an LSL outlet by mscheltienne in https://github.com/bsl-tools/bsl/pull/64
* Better handling of trigger metaclass by mscheltienne in https://github.com/bsl-tools/bsl/pull/65

**Full Changelog**: https://github.com/bsl-tools/bsl/compare/0.4.0...0.5.0

- Fix the recorder button on the StreamViewer.
- Improves the documentation, the crosslinks in the documentation and the examples.
- Reworks the trigger module.
- Package a version of pylsl and liblsl with BSL as a backup
- Improves CIs workflows
- Improves testing

fix readme with new API syntax for player and recorder.

- Improve API for StreamPlayer, StreamRecorder, StreamReceiver.
- Improve documentation.
- Improve examples.

Fix bug for python v3.6.x and v3.7.x.