[chore/bugfix] Switch markdown from blackfriday to goldmark (#1267)

Co-authored-by: Autumn! <autumnull@posteo.net>

vendor/github.com/yuin/goldmark/parser/emphasis.go

@@ -0,0 +1,50 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+)
+
+type emphasisDelimiterProcessor struct {
+}
+
+func (p *emphasisDelimiterProcessor) IsDelimiter(b byte) bool {
+	return b == '*' || b == '_'
+}
+
+func (p *emphasisDelimiterProcessor) CanOpenCloser(opener, closer *Delimiter) bool {
+	return opener.Char == closer.Char
+}
+
+func (p *emphasisDelimiterProcessor) OnMatch(consumes int) ast.Node {
+	return ast.NewEmphasis(consumes)
+}
+
+var defaultEmphasisDelimiterProcessor = &emphasisDelimiterProcessor{}
+
+type emphasisParser struct {
+}
+
+var defaultEmphasisParser = &emphasisParser{}
+
+// NewEmphasisParser return a new InlineParser that parses emphasises.
+func NewEmphasisParser() InlineParser {
+	return defaultEmphasisParser
+}
+
+func (s *emphasisParser) Trigger() []byte {
+	return []byte{'*', '_'}
+}
+
+func (s *emphasisParser) Parse(parent ast.Node, block text.Reader, pc Context) ast.Node {
+	before := block.PrecendingCharacter()
+	line, segment := block.PeekLine()
+	node := ScanDelimiter(line, before, 1, defaultEmphasisDelimiterProcessor)
+	if node == nil {
+		return nil
+	}
+	node.Segment = segment.WithStop(segment.Start + node.OriginalLength)
+	block.Advance(node.OriginalLength)
+	pc.PushDelimiter(node)
+	return node
+}