add StructIO

[baggepinnen]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

Add input and output connectors corresponding to symbolic structs

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 21 lines in your changes are missing coverage. Please review.

Project coverage is 0.00%. Comparing base (d504fa8) to head (5401a99).
Report is 25 commits behind head on main.

Files	Patch %	Lines
src/Blocks/utils.jl	0.00%	21 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #265   +/-   ##
=====================================
  Coverage   0.00%   0.00%           
=====================================
  Files         35      35           
  Lines       1615    1647   +32     
=====================================
- Misses      1615    1647   +32     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.