[Cthulhu7th] 技能ロールで難易度を指定可能にする

[ysakasin]

・技能ロールの難易度指定　CC(x)<=(目標値)(難易度)
　目標値の後に難易度を指定することで
　成功／失敗／クリティカル／ファンブル を自動判定する。
　難易度の指定：
　　r:レギュラー　h:ハード　e:イクストリーム　c:クリティカル
　例）CC<=70r CC1<=60h CC-2<=50e CC2<=99c

[codecov]

Codecov Report

Merging #417 (6bfb12b) into master (745f1bb) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 6bfb12b differs from pull request most recent head f8e941a. Consider uploading reports for the commit f8e941a to get more accurate results

@@           Coverage Diff           @@
##           master     #417   +/-   ##
=======================================
  Coverage   95.07%   95.08%           
=======================================
  Files         284      284           
  Lines       18519    18540   +21     
=======================================
+ Hits        17607    17628   +21     
  Misses        912      912           

Impacted Files	Coverage Δ
lib/bcdice/game_system/Cthulhu7th.rb	99.28% <100.00%> (+0.12%)	⬆️

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