Remove NXXM. Execute IWYU. (ArthurSonzogni#397)

Move to v2.0.0 (ArthurSonzogni#315)

Merge workflows. (ArthurSonzogni#234)

- Merge all the workflows into one file.
- Produce Windows and MacOS artifact.

Fix workflow

Add Changelog. (ArthurSonzogni#213)

- Increase version to 0.9
- Add a changelog.

From now one. Developpement happens on the `dev` branch.

See: ArthurSonzogni#207