column builder - Rename Virtual() to AsVirtual() and Column() to AsColumn()

[Insei]

• replace example project to examples directory

[codecov-commenter]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 75.48%. Comparing base (40c5e61) to head (b9ed9f1).
⚠️ Report is 39 commits behind head on main.

Files with missing lines	Patch %	Lines
column.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #17   +/-   ##
=======================================
  Coverage   75.48%   75.48%           
=======================================
  Files          55       55           
  Lines        1799     1799           
=======================================
  Hits         1358     1358           
  Misses        408      408           
  Partials       33       33           

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