register slot locks in visualizations

[sagnikpal2004]

Added locks drawn over register slots to show that they are locked.
All functionality, including updating the plot with notify works.

• The code is properly formatted and commented.
• Substantial new functionality is documented within the docs.
• All new functionality is tested.
• All of the automated tests on github pass.
• Formatting

Notes:

• The marker is probably not very visible. The color may be changed, or it can be drawn to the side (but drawing to the side causes line segments to be drawn over them)
  Lock to the side (one second change, not committed)

  
  

Closes #95

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 64.65%. Comparing base (fea11cc) to head (e1df176).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
ext/QuantumSavoryMakie/QuantumSavoryMakie.jl	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #241      +/-   ##
==========================================
- Coverage   72.58%   64.65%   -7.93%     
==========================================
  Files          52       52              
  Lines        2006     2006              
==========================================
- Hits         1456     1297     -159     
- Misses        550      709     +159     

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