feat(core): add c3 plus

[Meow404]

This change is 

[github-actions]

LCOV of commit 7fc02ca during C3 Coverage #55

Summary coverage rate:
  lines......: 92.4% (1416 of 1533 lines)
  functions..: 77.2% (129 of 167 functions)
  branches...: 52.3% (1175 of 2248 branches)

Files changed coverage rate:
                                        |Lines       |Functions  |Branches    
  Filename                              |Rate     Num|Rate    Num|Rate     Num
  ============================================================================
  core/c3.cc                            | 7.8%    282|2257%    21|    -      0
  core/c3.h                             |14.3%     21|2100%     2|    -      0
  core/c3_miqp.cc                       | 2.7%     73|    #     2|    -      0
  core/c3_options.h                     | 1.5%     66|4400%     1|    -      0
  core/c3_plus.cc                       | 8.1%     62|1880%     5|    -      0
  core/c3_plus.h                        | 200%      1| 0.0%     2|    -      0
  core/c3_qp.cc                         | 6.1%     33|4300%     2|    -      0
  core/lcs.cc                           |14.0%     50|1100%     6|    -      0
  core/lcs.h                            |18.8%     16|2600%     3|    -      0
  core/test/c3_cartpole_problem.hpp     | 2.8%     72|5300%     2|    -      0
  multibody/geom_geom_collider.cc       |12.6%     87| 545%    11|    -      0
  multibody/lcs_factory.cc              | 4.9%    307|3467%    15|    -      0
  multibody/lcs_factory.h               |33.3%      3|1200%     1|    -      0
  multibody/lcs_factory_options.h       | 7.7%     26| 800%     2|    -      0
  systems/c3_controller.cc              | 4.5%    110|3040%     5|    -      0
  systems/c3_controller_options.h       |12.5%     16|2400%     1|    -      0
  systems/framework/c3_output.h         |36.4%     11| 667%     3|    -      0
  systems/lcs_factory_system.cc         |14.7%     34|1250%     4|    -      0
  systems/lcs_factory_system.h          |50.0%      8| 0.0%     4|    -      0

[xuanhien070594]

bindings/pyc3/c3_multibody_py.cc line 95 at r1 (raw file):

}  // namespace pyc3
}  // namespace multibody
}  // namespace c3

Missing end line