Add nlopt as extra peg it

[boverhof]

Fixes/Addresses:

#1273

Summary/Motivation:

Add extras dependency so can peg nlopt to a version that is compatible with FOQUS matplotlib 2.7.5/numpy

Changes proposed in this PR:

• setup.py add nlopt to extras

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 39.89%. Comparing base (57fb2e2) to head (49bf399).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1274      +/-   ##
==========================================
+ Coverage   39.87%   39.89%   +0.02%     
==========================================
  Files         165      165              
  Lines       37747    37747              
  Branches     5865     5865              
==========================================
+ Hits        15052    15060       +8     
+ Misses      21597    21587      -10     
- Partials     1098     1100       +2     

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[sotorrio1]

LGTM