submark-0.3.1: Extract a part from CommonMark/Markdown docs

Index

caseInsensitiveText.CommonMark.Sub
extractSectionText.CommonMark.Sub
flattenInlineNodesText.CommonMark.Sub
headingLevelText.CommonMark.Sub
HeadingPattern 
1 (Type/Class)Text.CommonMark.Sub
2 (Data Constructor)Text.CommonMark.Sub
HeadingTitlePatternText.CommonMark.Sub
HeadingTitleRegexText.CommonMark.Sub
HeadingTitleTextText.CommonMark.Sub
LevelText.CommonMark.Sub
matchesHeadingText.CommonMark.Sub
titlePatternText.CommonMark.Sub