release: bump all packages to 0.1.1, add PyPI metadata and CHANGELOG

- Add readme field to all three pyproject.toml files (populates PyPI description page)
- Bump versions to 0.1.1 and update behave-core pin in shell/text
- Update Install sections in root, BEHAVE-SHELL, and BEHAVE-TEXT READMEs to lead with pip install from PyPI
- Add CHANGELOG.md at project root (Keep-a-Changelog format)

BEHAVE-TEXT/README.md

@@ -19,8 +19,12 @@ is deliberately neutral: BEHAVE-TEXT observes actors, not adversaries.
 ## Install
 
 ```bash
-pip install -e ../core/ -e .
-# development:
+pip install behave-text
+```
+
+For local development:
+
+```bash
 pip install -e ../core/ -e ".[dev]"
 ```