Extension methods for kana conversion.

• ToRomaji() - convert Hiragana (ひらがな) or Katakana (カタカナ) to romaji.

var romaji = "ひらがな・カタカナ".ToRomaji(); // result "hiraganakatakana"

StringBuilder with Microsoft.Extensions.ObjectPool

using Microsoft.Extensions.ObjectPool;

var stringBuilderPool = new DefaultObjectPoolProvider()
	.CreateStringBuilderPool();

for (var i = 0; i < 1_000_000; i++)
{
	var romaji = "ひらがな・カタカナ".ToRomaji(stringBuilderPool);
}

Benchmark

Convert a kana string of 1,000,000 characters to romaji.

Method	Mean	Error	StdDev	Gen0	Gen1	Gen2	Allocated
MyNihongo	9.756 ms	0.1463 ms	0.1368 ms	984.3750	984.3750	984.3750	7.54 MB
MyNihongoMultiple	962.581 ms	7.2602 ms	6.7912 ms	99000.0000	99000.0000	99000.0000	754.29 MB
WanaKana_Sharp	11.545 ms	0.1239 ms	0.1159 ms	796.8750	781.2500	484.3750	7.62 MB
WanaKana_SharpMultiple	1,147.683 ms	14.6285 ms	12.9678 ms	80000.0000	79000.0000	49000.0000	761.87 MB

WanaKana_Net (1.0.0) threw a StackOverflow exception.