Fix find_package for curl

[bgs99]

Fixes the find_package call to point to the curl module provided by CMake (https://cmake.org/cmake/help/latest/module/FindCURL.html)

Without this change, building via CMake produces the following error:

  CMake Error at test/CMakeLists.txt:27 (find_package):
  By not providing "Findcurl.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "curl", but
  CMake did not find one.

  Could not find a package configuration file provided by "curl" with any of
  the following names:

    curlConfig.cmake
    curl-config.cmake

  Add the installation prefix of "curl" to CMAKE_PREFIX_PATH or set
  "curl_DIR" to a directory containing one of the above files.  If "curl"
  provides a separate development package or SDK, be sure it has been
  installed.

[bgs99]

As a side note, what do you think about adding a CMake (and also Meson, I guess) pipeline in CI?

At least just for building the tests without running them.

[yhirose]

Thanks!