Add basic Gitea Actions CI workflow
CI / pre-commit (pull_request) Successful in 56s
CI / build (-DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++, clang-arm64, ubuntu-latest-arm64) (pull_request) Successful in 2m25s
CI / build (-DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++, clang-amd64, ubuntu-latest-amd64) (pull_request) Successful in 2m52s
CI / build (-DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++, gcc-arm64, ubuntu-latest-arm64) (pull_request) Successful in 2m45s
CI / build (-DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++, gcc-amd64, ubuntu-latest-amd64) (pull_request) Successful in 3m7s