Add linting

[ianthomas23]

Add automated linting of C++ code. This should be done as soon as possible, before we have written a lot of code.

[nakul-py]

@ianthomas23 we can use these core tools for automated linting:

• clang-format: for linting/formatting code.
• clang-tidy: catches bugs, modernizations, style issues, and static-analysis-like warnings.
• pre-commit: framework to run linting/formatting locally before commits.
• CI integration: run checks on pull requests

[ianthomas23]

Thanks @nakul-py; I think everyone here is aware of the possibilities.

[ianthomas23]

Closed by #121.