* Tests: add detection coverage for UTF7 with BOM

This means that it would never provide detection of UTF7 at
runtime, because the other prefix would always take priority.

* 🐛 Allow UTF7 BOM to detect empty-content case

Checking for this special-case UTF7 BOM before the other cases
allows us to detect an empty document, which Python 3 encodes
into ASCII with a trailing minus symbol ('-').

close #719

Bumps [pypa/cibuildwheel](https://github.com/pypa/cibuildwheel) from 3.3.1 to 3.4.0.
- [Release notes](https://github.com/pypa/cibuildwheel/releases)
- [Changelog](https://github.com/pypa/cibuildwheel/blob/main/docs/changelog.md)
- [Commits](pypa/cibuildwheel@298ed2f...ee02a15)

---
updated-dependencies:
- dependency-name: pypa/cibuildwheel
  dependency-version: 3.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [docker/setup-qemu-action](https://github.com/docker/setup-qemu-action) from 3.7.0 to 4.0.0.
- [Release notes](https://github.com/docker/setup-qemu-action/releases)
- [Commits](docker/setup-qemu-action@c7c5346...ce36039)

---
updated-dependencies:
- dependency-name: docker/setup-qemu-action
  dependency-version: 4.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 8.0.0 to 8.0.1.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@70fc10c...3e5f45b)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: 8.0.1
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [github/codeql-action](https://github.com/github/codeql-action) from 4.32.4 to 4.35.1.
- [Release notes](https://github.com/github/codeql-action/releases)
- [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md)
- [Commits](github/codeql-action@89a39a4...c10b806)

---
updated-dependencies:
- dependency-name: github/codeql-action
  dependency-version: 4.35.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

close #718
linked to #716

Release 3.4.7