Flowsheet documentation for NaCl crystallizer

[OOAmusat]

Fixes/Resolves:

NaCl crystallizer flowsheet documentation for #1219

Summary/Motivation:

Adding NaCl crystallizer flowsheet documentation

Changes proposed in this PR:

• Only includes adding .rst for the NaCl crystallizer example

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[MarcusHolly]

A few minor comments to address

[MarcusHolly]

LGTM

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.02%. Comparing base (3cf1fb8) to head (0ab70ad).
Report is 57 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1403   +/-   ##
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  Coverage   94.02%   94.02%           
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  Files         335      335           
  Lines       35620    35620           
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  Hits        33491    33491           
  Misses       2129     2129           

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[MarcusHolly]

One more thing I missed in my review - you should also provide a link here to the crystallization property package. Although it looks like there's no documentation for this yet... I think it'd be nice to have this for the 1.0 release, so maybe it's best to address this in a separate PR that also adds the prop pack documentation.