feat: use strings.Builder to save memory

[apocelipes]

Fixes #649.

[codecov]

Codecov Report

Attention: Patch coverage is 96.93878% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 81.12%. Comparing base (1a9d517) to head (ac5dc58).
Report is 1 commits behind head on master.

Files	Patch %	Lines
bulletlist_printer.go	80.00%	2 Missing ⚠️
interactive_select_printer.go	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #650      +/-   ##
==========================================
+ Coverage   81.05%   81.12%   +0.06%     
==========================================
  Files          33       33              
  Lines        4176     4196      +20     
==========================================
+ Hits         3385     3404      +19     
- Misses        718      719       +1     
  Partials       73       73              

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