feat: allow game to be character vector if output is a pdf

[trevorld]

• The game argument of save_pamphlet() and save_ruleset() can now be a character vector of games when the target output is a pdf file.
• save_pamphlet(), save_rulebook(), and save_ruleset() now return the path to the generated file silently.

closes #1

[codecov]

Codecov Report

❌ Patch coverage is 95.14563% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.31%. Comparing base (9f96437) to head (21ef0c1).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
R/rules.R	95.14%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #41      +/-   ##
==========================================
+ Coverage   86.64%   89.31%   +2.67%     
==========================================
  Files           7        7              
  Lines         599      674      +75     
==========================================
+ Hits          519      602      +83     
+ Misses         80       72       -8     

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