add brief tutorial on delay systems

[baggepinnen]

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[JuliaControlBot]

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Plots were compared to references. 8/11 images have changed, see differences below.
After pulling this PR, please update the reference images by creating a PR to ControlExamplePlots.jl here.

Difference	Reference Image	New Image
❌ 0.048
✔️ 0.0
✔️ 0.001
✔️ 0.001
✔️ 0.0
❌ 0.043
❌ 0.059
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[codecov]

Codecov Report

Merging #704 (f5758fb) into master (48de82b) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #704   +/-   ##
=======================================
  Coverage   87.91%   87.91%           
=======================================
  Files          35       35           
  Lines        3624     3624           
=======================================
  Hits         3186     3186           
  Misses        438      438           

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