.clang-format and .pre-commit

[nkoukpaizan]

Description

Code formatting configuration files with CI support to apply the changes.
To replace PRs #82 and #151.
Addresses issues #5, #54 and #150.

Proposed changes

Added clang-format and pre-commit files.

Checklist

Put an x in the boxes that apply. You can also fill these out after creating
the PR. If you're unsure about any of them, don't hesitate to ask. We're here
to help! This is simply a reminder of what we are going to look for before
merging your code.

• All tests pass. Code tested on
  • CPU backend
  • CUDA backend
  • HIP backend
• Code compiles cleanly with flags -Wall -Wpedantic -Wconversion -Wextra.
• The new code follows Re::Solve style guidelines.
• There are unit tests for the new code.
• The new code is documented.
• The feature branch is rebased with respect to the target branch.

Further comments

Currently not applying the pre-commit changes. This is first to test the pipeline.

[superwhiskers]

my only comment is that to completely supplant #151, you should also delete these lines from CMakeLists.txt.