Add in End-to-End Test

[AyrtonB]

Every time a merge to main is made the new LOWESS model should be tested to ensure the program runs and that the values are correct.

Could use the original values from Cleveland's Fortran code for the check:

*        X values:
*          1  2  3  4  5  (10)6  8  10  12  14  50
* 
*        Y values:
*           18  2  15  6  10  4  16  11  7  3  14  17  20  12  9  13  1  8  5  19
* 
* 
*        YS values with F = .25, NSTEPS = 0, DELTA = 0.0
*         13.659  11.145  8.701  9.722  10.000  (10)11.300  13.000  6.440  5.596
*           5.456  18.998
* 
*        YS values with F = .25, NSTEPS = 0 ,  DELTA = 3.0
*          13.659  12.347  11.034  9.722  10.511  (10)11.300  13.000  6.440  5.596
*            5.456  18.998
* 
*        YS values with F = .25, NSTEPS = 2, DELTA = 0.0
*          14.811  12.115  8.984  9.676  10.000  (10)11.346  13.000  6.734  5.744
*            5.415  18.998