Standalone emoji support

[jquast]

CLoses #133 and #154.

This decreases general performance by ~10% for complex CJK/combining and emoji strings.

• Regional Indicator pairs measured as one 2-cell flag; unpaired RI measured individually
• Fitzpatrick skin tone modifiers are zero-width when following an emoji base, Narrow when "standalone"

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will degrade performance by 22.14%

_{Comparing jq/standalone-modifiers (7e265fa) with master (8c8eac8)}

Summary

❌ 8 regressed benchmarks
✅ 48 untouched benchmarks
🆕 4 new benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
🆕	test_wcswidth_ri_flags_unpaired	N/A	87.9 ms	N/A
❌	test_width_udhr_lines	263 ms	294.5 ms	-10.7%
❌	test_width_wcswidth_consistency_udhr	386.8 ms	440.5 ms	-12.21%
🆕	test_wcswidth_ri_flags_paired	N/A	371.5 ms	N/A
❌	test_ljust_udhr_lines	265.9 ms	297.4 ms	-10.61%
🆕	test_width_ri_flags_paired	N/A	371.7 ms	N/A
❌	test_width_composed	1.6 ms	1.9 ms	-12.85%
❌	test_wcswidth_long_japanese	231 µs	267.1 µs	-13.52%
❌	test_wcswidth_composed	1.4 ms	1.7 ms	-14.5%
❌	test_wcswidth_decomposed	2.2 ms	2.4 ms	-10.57%
❌	test_wcswidth_emoji_sequence	47.4 µs	60.8 µs	-22.14%
🆕	test_width_ri_flags_unpaired	N/A	88 ms	N/A

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (8c8eac8) to head (7e265fa).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #202   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           15        15           
  Lines          896       938   +42     
  Branches       227       239   +12     
=========================================
+ Hits           896       938   +42     

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