Add modelling tutorials

[odow]

Part of #2483

It's got a QP as part of it though. Preference for splitting into two tutorials and forming a QP subdirectory?

Preview: https://jump.dev/JuMP.jl/previews/PR2489/index.html

[codecov]

Codecov Report

Merging #2489 (50396c0) into master (16426d9) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2489   +/-   ##
=======================================
  Coverage   92.40%   92.40%           
=======================================
  Files          43       43           
  Lines        4677     4677           
=======================================
  Hits         4322     4322           
  Misses        355      355           

---

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 16426d9...885cf2e. Read the comment docs.

[odow]

Merging since these were mostly just copied from JuMPTutorials. Please comment on #2483 if you see things that need to be fixed, or make a PR.