tipi.build generated CMakelists

[daminetreg]

Dear @CallForSanity,

As I went on your profile and saw the CMake support for the fun libcity library, I thought why not try it with tipi. I've let tipi build the tests as well, as the existing cmake did not include the test folder.

Here I propose a change to use libcity with tipi easily, it also enable depending on libcity in another project by simply adding the following to .tipi/deps:

{
  "CallForSanity/libcity": { }
}

I also added auto-generated CI support with the command tipi ci on github actions and fixed some const correctness topics pointed out by libc++.

The generated CMakeLists are put in build/<target>/recipe/CMakeLists.txt at build time and hence it would also be possible to delete the hand written cmake.

Do you think I should try Pull-Requesting it to the upstream ? 😄