Support dot-based getproperty in ljl_propfunc

[oschulz]

Also add support for square-brackets index access, the conditional ternary operator and functions one, zero and identity.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 7 lines in your changes missing coverage. Please review.

Project coverage is 41.96%. Comparing base (3bf5c54) to head (c835c1f).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/ljl_expressions.jl	66.66%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #83      +/-   ##
==========================================
+ Coverage   41.76%   41.96%   +0.19%     
==========================================
  Files          26       26              
  Lines        1942     1959      +17     
==========================================
+ Hits          811      822      +11     
- Misses       1131     1137       +6     

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