defined ackley function and fixed plotting problem

[RohitRathore1]

No description provided.

[codecov]

Codecov Report

Merging #213 into master will increase coverage by 0.23%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #213      +/-   ##
==========================================
+ Coverage   84.83%   85.06%   +0.23%     
==========================================
  Files          20       20              
  Lines        1734     1734              
==========================================
+ Hits         1471     1475       +4     
+ Misses        263      259       -4     

Impacted Files	Coverage Δ
src/Optimization.jl	90.45% <0.00%> (+0.70%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 631e4ca...a856e60. Read the comment docs.