[Feature] 希望可以增加弹幕覆盖程度配置项

[zhaoge0202]

Is your feature request related to a problem? Please describe.

当前是全屏覆盖的，体验观感并不好’
无法控制弹幕显示区域，导致重要画面内容被遮挡

Describe the solution you'd like

允许用户设置弹幕显示的最大行数（如3行）
可以指定弹幕仅在屏幕上方特定区域显示

在配置文件中添加弹幕显示控制参数
限制弹幕仅在指定区域内滚动
提供简单的配置项供用户配置

Describe alternatives you've considered

弹幕密度控制

Additional context

(Add any other context or screenshots about the feature request here.)

[lululutx]

给您参考一下我的配置， 其他配置项 #142

src/burn/generate_danmakus.py Ln76
subprocess.run([DanmakuFactory_PATH, "-o", in_ass_path, "-i", in_xml_path, "--resolution", resolution, "--msgboxsize", boxsize, "--msgboxfontsize", boxfont, "-S", danmakufont, "--scrollarea" ,"0.3","-O" ,"180","-d", "-1" , "--ignore-warnings"])