feat: Publish individual drivers to PyPI as micropython-steami-* packages.

[nedseb]

Description

Publish each driver as a separate PyPI package so developers can `pip install micropython-steami-bme280` into their venv for IDE autocompletion and type checking.

Context

While `mip` (#338) is the primary on-device distribution channel, PyPI is useful for:

• IDE autocompletion (Pylance, Pyright) without manual stub setup
• CI/CD pipelines that need to lint or test against driver APIs
• Discoverability in the broader Python ecosystem

Naming convention

`micropython-steami-` (standard `micropython-` prefix + `steami-` namespace)

Examples: `micropython-steami-bme280`, `micropython-steami-ism330dl`, `micropython-steami-ssd1327`

Tasks

• Create `lib//pyproject.toml` for each driver with PyPI metadata
• Add `Programming Language :: Python :: Implementation :: MicroPython` classifier
• Create PyPI account/organization for the project
• Add PyPI API token as GitHub Actions secret
• Add publish job to `.github/workflows/release.yml` that builds and uploads wheels after semantic-release
• Update version sync (ci: Sync driver versions on release via semantic-release. #339) to include per-driver `pyproject.toml`
• Test: `pip install micropython-steami-bme280` → `from bme280 import BME280` works

Depends on

• feat: Add mip package.json for all drivers. #338 (mip package.json — do this first)
• ci: Sync driver versions on release via semantic-release. #339 (version sync)