This Pull Request updates some of our CI config and adds config for bors.
It changes the following:
- remove `cargo check` from CI (`cargo test` should be enough)
- change back to `cargo tarpaulin` on Linux to get coverage information
- simplify some of the CI steps' names
- add workflow for bors
##### Working with bors
It's setup so that we need 2 approvals before we can merge like we discussed in Discord.
After the second approval we can write a comment with `bors r+` so that the merge is tested.
bors will only run if `test`, `rustfmt`, `clippy`, `examples` and `doc` are all running error free in the PR's branch. It will then run them again in a `staging` branch that is the equivalent of merging the PR on `main`.
Another option we can consider is `up_to_date_approvals`, so that new commits make previous approvals not count.
The bors reference can be found here: https://bors.tech/documentation/