Release v0.7.0

In this release of eldim you can find the following changes:

* Significant reliability and stability improvements
* Several bug fixes
* Improved systemd unit file with optional sandboxing
* Improved TLS configuration, including Post-Quantum TLS
* Better handling of race conditions with the same file name and host
* Improved and structured logging (vs plaintext before): -j is more useful!
* Reduced and updated dependencies of eldim

Breaking changes:

* File names can no longer contain \0, ., .., starting, trailing, or
consecutive /'s.
* The logging format has changed, it's now structured vs text, explore -j!

Add GitHub action to build Debian packages