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

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

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

@@ -0,0 +1,42 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type autoLinkParser struct {
+}
+
+var defaultAutoLinkParser = &autoLinkParser{}
+
+// NewAutoLinkParser returns a new InlineParser that parses autolinks
+// surrounded by '<' and '>' .
+func NewAutoLinkParser() InlineParser {
+	return defaultAutoLinkParser
+}
+
+func (s *autoLinkParser) Trigger() []byte {
+	return []byte{'<'}
+}
+
+func (s *autoLinkParser) Parse(parent ast.Node, block text.Reader, pc Context) ast.Node {
+	line, segment := block.PeekLine()
+	stop := util.FindEmailIndex(line[1:])
+	typ := ast.AutoLinkType(ast.AutoLinkEmail)
+	if stop < 0 {
+		stop = util.FindURLIndex(line[1:])
+		typ = ast.AutoLinkURL
+	}
+	if stop < 0 {
+		return nil
+	}
+	stop++
+	if stop >= len(line) || line[stop] != '>' {
+		return nil
+	}
+	value := ast.NewTextSegment(text.NewSegment(segment.Start+1, segment.Start+stop))
+	block.Advance(stop + 1)
+	return ast.NewAutoLink(typ, value)
+}